2020 fire and explosives investigation [autosaved] [autosaved]

FIRE AND EXPLOSIVES INVESTIGATION
JULY –DEC 2021 SEM
BY Col (Rtd) D.W Theuri
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Dedan Kimathi University of Technology
Better Life Through Technology
Introduction
 Fire has been the oldest human invention in history (Gowlett,2016)
 Fire has also been the most widely used technology on a global scale (Keely, 2009)
 Despite fire having many technological benefits in human life, it is also present many
technological hazards in human life
 The fire science of combustion and management of its hazards are poorly understood
globally scale despite fire being the most widely used technology.
 The destructive characteristics of fire makes it’s a suitable choice for committing criminal and
malicious act.
 This lesson: Fire investigation will shade light on the science of fire combustion and issues to
look for in investigating arson (U.S Department of Justice, 2000)
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ThE Methodology of fire & arson invest
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Methodology of bomb & Explosives investigation
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Objectives of fire investigation
 To develop an opinion about the fire origin
 To determine the "cause of the fire“ and to prevent future incidences
 Other investigators investigate to determine losses and subrogation options for claims purposes
 The objective of many local fire investigations is to comply with the law requiring investigations or even the determination of cause.
 Some investigations are conducted to satisfy political or social or legal demands
 Some investigations are conducted to determine violations of the law or regulations
 Some are even conducted to determine if present codes and standards are adequate.
 Thoughtful analysis of these objectives suggests that almost all demand opinions of the investigator.
 None of these objectives address directly the addition of new knowledge on which persons with fire safety responsibilities must act in the
future.
What should be the objective of a fire investigation ? What theoretical basis, - that is what concepts and principles - should govern the
setting of fire investigation objectives? How should the investigation objectives be framed so success or failure of an investigation can be
measured?
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Arson and explosive incidence motives
• The motives for arson are quite diverse and well known. They include:
 Profit in form of payment for services rendered or seeking compensation
 Revenge and jelousy
 Spite (annoy/provoke)
 crime concealment,
 intimidation,
 vandalism,
 excitement,
 pyromania.
 Terrorism
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What is fire
 Fire is a chemical reaction in which the oxygen from the air is combined with a gaseous or vaporous fuel (Even
if the fuel is a solid eg wood, or liquid like petrol,) in presence of heat to produce ignition and subsequent
combustion .
 It is the vapours given off when the fuel is heated that burns. This rapid oxidation produces heat and light.
 Fire can usually take place when three elements are present i.e oxygen, fuel and heat.
 Oxygen. It is readily available from the atmosphere, and it makes 21% of the air we breathe.
 Fuel.
 It comprises solid combustibles like paper, furniture, clothing and plastics
 Flammable liquids like petrol, oils, paints, cooking oils and fats
 Flammable gases like natural gas , LPG and acetylene
 Heat. The heat is given off by the oxidation reaction that sustains the fire burning. First, a heat source is required to produce ignition. Ignition
sources include :
 Heating and cooking appliances ; Faulty electrical equipment’s, Cigarette lighters and matches, Friction etc
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Combustion and principles of combustion
 Combustion: Is the process of burning when fuel is combined with oxygen in presence of appropriate heat to produce carbon dioxide and
water.
 Combustion is an exothermic reaction, so it releases heat, but sometimes the reaction proceeds so slowly that a temperature change is not
noticeable.
 Good signs that you are dealing with a combustion reaction include the presence of oxygen as a reactant and carbon dioxide, water and heat
as products.
 The principles of fire :
 There must be an oxidizing agent, combustible material and a source of ignition for combustion to take place
 Combustible materials must be heated to ignition temperatures before it will burn
 Combustion continues until:
o Combustible material is removed or consumed
o The oxidation agent concentration is lowered below essential levels
o The combustible material is cooled below the ignition temperatures
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Heat energy sources
 Heat is produced in the following manner through chemical process :
o Combustion. The heat is generated through the process of oxidation. The heat energy produced by combustion is used for various
functions like domestic and industrial usage for purposes of heating or cooking. The heat energy is available subject to availability
of oxygen or air supply
o Spontaneous heat. All organic substances are capable of combining with oxygen at some critical temperatures with the evolution
of heat
o Decomposition
 Electrical Energy. Electrical heat energy is produced when electric current passes through a conductor or when a spark jumps a gap
 Static Electricity . Also known as friction electricity. It occurs due to accumulation of charges on the surface of materials that have
been brought together and the separated
 Lightening. Discharge of electrical charges on a cloud
 Mechanical heat energy through friction and heat compression
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Classes of fire
 Class A . Class A refers to fires that burn organic materials to ash. Combustible materials that fall under this type of fire include wood,
trash, non-melting plastic, rubber, paper and cloth. The type of fire extinguisher you use to put out a fire depends on what class of fire you
are attempting to extinguish. You can extinguish a Class A fire with a water fire extinguisher, which contains air-pressurized water that
successfully snuffs out flames.
 Class B. Class B fires burn flammable liquid, gas and melting plastic. Class B combustible materials include gasoline, propane, paint
thinner, kitchen grease and oil. If you face a Class B fire, use a dry chemical or a carbon dioxide fire extinguisher to put it out. Dry
chemical extinguishers contain foam or powder, while carbon dioxide extinguishers contain highly-pressurized carbon dioxide. You should
use a dry chemical or a carbon dioxide fire extinguisher to put out grease fires, but never use water fire extinguishers on grease.
 Class C. Class C fires involve electrical equipment. Class C combustible materials include electrical outlets, appliances, circuit breakers
and wiring. You can suffer from an electrical shock if you attempt to use water to put out an electrical fire. Instead, use dry chemical or
powder fire extinguishers when confronting Class C fires. Use a carbon dioxide fire extinguisher on a Class C fire involving electronics,
such as TVs and computers, since a powder extinguisher can leave a damaging residue.
 Class D .Class D pertains to unusual fires that occur with certain flammable metals such as magnesium, sodium, titanium, aluminum
and potassium. Extinguish Class D fires by using only Class D fire extinguishers, which often contain sodium chloride. Use a powdered
copper metal fire extinguisher on a Class D fire that involves flammable lithium and lithium all oys. Class D fires do not react well to
water, and it is very dangerous to attempt to put them out with extinguishers that are not labeled Class
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Role of water in fire fighting
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surface cooling: Prevention of fuel pyrolysis by removing heat energy from the fuel source when water evaporates
 gas cooling or smoke cooling. The lowering of gas and smoke temperature when water vapour mixes with polysized gases
during combustion
 There also exist cases where the ignition factor is not the activation energy. For example, smoke explosion is a very violent
combustion of unburned gases contained in the smoke created by a sudden fresh air input (oxidizer input). The interval in
which an air/gas mix can burn is limited by the explosive limits of the air. This interval can be very small (kerosene) or large
(acetylene).
 Water cannot be used on certain type of fires:
 Fires where live electricity is present — as water conducts electricity it presents an electrocution hazard.
 Hydrocarbon fires — as it will only spread the fire because of the difference in density.
 Metal fires — as these fires produce huge amounts of energy (up to 7.550 calories/kg for aluminum) and water can also
create violent chemical reactions with burning metal (by oxidization) .
 Oil fires — as vapour will carry and spread burning oil everywhere.

Fire extinguishing agents
 A fire extinguisher is an active fire protection device used to extinguish or control
small fires, often in emergency situations.
 Typically, a fire extinguisher consists of a hand-held cylindrical pressure vessel containing
an agent that can be discharged to extinguish a fire. Examples of such agents include:
 Dry Powder .This is a powder-based agent that extinguishes fire by separating the four parts
of the fire tetrahedron. It prevents the chemical reactions involving heat, fuel, and oxygen and
halts the production of fire sustaining "free-radicals", thus extinguishing the fire. Examples
of such chemicals are :
 Foams . It is Applied to fuel fires as either an aspirated (mixed & expanded with air in a branch
pipe) or non-aspirated form to form a frothy blanket or seal over the fuel, preventing oxygen
reaching it. Unlike powder, foam can be used to progressively extinguish fires without
flashback.
 Water. Cools burning material (surface cooling & gas cooling)

Extinguishing agent cont.
 Wet chemical and water additives. Wet Chemical (potassium acetate, carbonate,
or citrate) extinguishes the fire by forming a soapy foam blanket over the burning oil
and by cooling the oil below its ignition temperature. Generally class A and K (F in
Europe) only, although newer models are outfitted with misting nozzles as those used
on water mist units to give these extinguishers class B and C firefighting capability.
 Clean agents and carbon dioxide . These Agent displaces oxygen (CO2 or inert
gases), removes heat from the combustion zone or inhibits chemical chain reaction
.They are labelled clean agents because they do not leave any residue after discharge
which is ideal for sensitive electronics and documents.
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Fire extinguishers colour codes & Heat spread
 Red .For water as an extinguishing agent
 Cream : For foam
 Blue :Dry powder
 Bon dioxide Black : For car
 Yellow : For wet chemicals
 Heat produced by a fire can spread in one of three ways; convection, conduction and
radiation. Convection is the transfer of heat through air circulation, and only occurs in
liquids and gases. An example of convection is the heat from a fire rising and heating the
ceiling of a room. Conduction is the transfer of heat through a medium by direct contact,
such as a fire heating a metal beam which transfers the heat elsewhere. Radiation is the
emission of heat as infrared radiation without a medium.
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The behaviour of fire in a house (enclosure)
 Fire grows in stages: incipient, growth, fully developed and decay as shown in the diagram
below:
 Flashover This is not a stage of development, but simply a rapid transition between the
growth and fully developed stages.
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critical fire behavior indicators
 Building Factors, Smoke, Air Track, Heat, and Flame (B-SAHF)
 B –SAHF: ability to integrate these factors in the process of reading the fire assist in assessing fire build up and dynamic risk
assessment.
 Smoke and Air Track: Smoke conditions and the pattern of smoke and air movement are two of the most important
indicators of fire behavior.
 The location and appearance of smoke can provide valuable cues related to the location of the fire, its burning regime (fuel or
ventilation controlled) and the stage of fire in various areas of the building.
 It is critical that firefighters begin their assessment of smoke and air track indicators from outside the building, but continue
this process on an ongoing basis from both the interior and exterior of the structure
 Heat: While heat cannot be observed directly, observation of the effect of heat on air track (velocity of smoke discharge), the
building or exposures, and sensation of changes in temperature can be significant fire behavior indicators.
 PPEs: It is important to remember that our personal protective equipment provides significant insulation and slows the transfer
of heat and resulting sensation of changes in temperature.
 Flame. Flaming combustion is often the most obvious or visible indicator observed by firefighters.
 However, do not get so focused on visible flames that you miss more important, but subtle building, smoke, air track, and heat
indicators.
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The Incipient stage
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 a plume comprising of buoyant gases and smoke is discharged in coherent manner.
 As the plume rises to the ceiling, fresh air is entrained into the plume.
 This air entrainment dilutes the smoke and decreases the plume temperature as it rises. Once the plume impinges on
the ceiling, the buoyant gases move laterally across the ceiling, are deflected down from the ceiling, and form a layer of
smoke known as a ceiling jet.
 The ceiling jet spreads beneath the ceiling until the walls of the enclosure confine it.
 As the ceiling jet spreads beneath the ceiling, it loses heat to the ceiling, causing the temperature of the gases in the
ceiling jet to decrease with radial distance from the fire plume.
 This diagram illustrates the explanation above
Fire seat Buoyant gases
Ceiling jet

Basics of incipient stage
 Fire ignition: requires heat, fuel, and oxygen.
 Once combustion begins, development of an incipient fire is largely dependent on the
characteristics and configuration of the fuel involved Air in the compartment provides
adequate oxygen to continue fire development.
 During this initial phase of fire development, radiant heat warms adjacent fuel and
continues the process of pyrolysis.
 A plume of hot gases and flame rises from the fire and mixes with the cooler air within the
room. This transfer of energy begins to increase the overall temperature in the room. As
this plume reaches the ceiling, hot gases begin to spread horizontally across the ceiling.
 As flames near the ceiling, the layer of hot gases becomes more clearly defined and
increases in volume and fire continue to grow more quickly.
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Behaviour of fire at the incipient stage
 Building. Size, contents, ventilation profile, and fire protection systems all have a significant influence on
potential fire development and should be considered regardless of the stage of fire development.
 Building factors (such as size and ventilation profile) influence how other fire behavior indicators will present.
 The building and its contents will also influence how quickly a fire will transition from incipient to growth
stage.
 Smoke. Smoke will be limited and there will not be a well-defined layer of hot gases in the upper area of the
compartment. If smoke is visible from the exterior volume, will generally be light in color and have limited
buoyancy.
 Air Track Air track is generally not a major factor in recognition of incipient stage fires. However, some light
smoke discharge and inward air movement may be observed from openings close to the fire location.
 Heat. Low (near ambient) temperature within the compartment, condensation may be visible on windows in or
near the fire compartment. Depending on the degree of insulation, a heat signature may or may not be visible
from the exterior
 Flame. Fire confined to a small area (i.e., the object of origin) and flames lower than
ceiling height.
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The growth stage
 If there is adequate oxygen within the compartment additional fuel will become involved and the heat release rate from the
fire will increase.
 gas temperatures within the compartment may be described as existing in two layers: A hot layer extending down from
the ceiling and a cooler layer down towards the floor.
 Convection resulting from plume and ceiling jet along with radiant heat from the fire and hot particulates in the smoke
increases the temperature of the compartment linings and other items in the compartment
 As gases within the compartment are heated, they expand and when confined by the compartment increase in pressure.
 Higher pressure in this layer causes it to push down within the compartment and out through openings.
 The pressure of the cool gas layer is lower, resulting in inward movement of air from outside the compartment.
 At the point where these two layers meet, as the hot gases exit through an opening, the pressure is neutral.
 The interface of the hot and cool gas layers at an opening is commonly referred to as the neutral plane.
 The fire can continue to grow through flame spread or by ignition of other fuel within the compartment. As flames in the
plume reach the ceiling, they will bend and begin to extend horizontally. Pyrolysis products and flammable byproducts of
incomplete combustion in the hot gas layer will ignite and continue this horizontal extension across the ceiling. As the
fire moves further into the growth stage, the dominant heat transfer mechanism within the fire compartment shifts from
convection to radiation. Radiant heat transfer increases heat flux (transfer of thermal energy) at floor level
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The Flash over phase
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The sudden transition of fire from a growth stage to fully developed fire.
When flashover occurs, there is a rapid transition to a state of total surface
involvement of all combustible material within the compartment.
In general, ceiling temperature in the compartment must reach 500o-600o C
(932o-1112o F) or the heat flux (a measure of heat transfer) to the floor of the
compartment must reach 15-20 kW/m2 (79.25 Btu/min/ft2)-105.67
Btu/min/ft2).
When flashover occurs, burning gases will push out openings in the
compartment (such as a door leading to another room) at a substantial
velocity.

Indicators of impending flash over
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 Building. Building Flashover can occur in all types of buildings. Building factors can influence how quickly a fire will reach
flashover (i.e., fire load, ventilation profile, thermal properties) and should be considered an integral part of ongoing risk
assessment.
 Smoke. Smoke indicators may or may not be visible from the exterior of the structure.
 However, smoke conditions indicating a developing fire are a warning sign of potential flashover. After making entry, the
presence of hot gases overhead and lowering of the hot gas layer are key indicators.
 Darkening smoke can be a flashover indicator, but do not depend on smoke color alone
 Air Track. A strong bi-directional (air in and smoke out) air track can be a significant indicator of Flashover that will move in
the direction of the opening.
 any air track that shows air movement into the fire can result in flashover.
 Increasing velocity of the air track when combined with other indicators can be a strong flashover indicator.
 Use of a thermal imaging camera (TIC) can allow more effective observation of convective heat currents within the building.

Indicators of impending flashover
 Heat. Outside the fire compartment, perception of increasing temperature may not provide reasonable warning of impending
flashover.
 However, perception of increasing temperature and observation of heat indictors such as pyrolysis of fuel packages some
distance from the fire should be considered as a strong indicator of worsening fire conditions and potential for flashover.
 Use of a TIC allows observation of increased temperature and may allow observation of flaming combustion within the hot gas
layer. Observation of the opening to the fire compartment will indicate high temperature at the top of the opening.
 From the exterior, increasing velocity of smoke discharge (an air track indicator) also indicates increasing temperature within
the building.
 A TIC may allow observation of a pronounced heat signature in the area of the fire compartment.
 Flame. Isolated flames traveling in the hot gas layer (ghosting) or more substantially through the gas layer or across the ceiling
(rollover). It is important to note that these flames may or may not be visible (without use of a thermal imaging camera). A
later (potentially too late) indicator of impending flashover is rollover moving along the ceiling of the fire compartment and
into adjacent spaces.
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Fully Developed Stage
 . At this post-flashover stage, energy release is at its greatest, but is generally limited
by ventilation
 Unburned gases accumulate at the ceiling level and frequently burn as they leave the
compartment, resulting in flames showing from doors or windows.
 The average gas temperature within a compartment during a fully developed fire
ranges from 700o – 1200o C (1292o – 2192o F)
 compartment where the fire started may reach the fully developed stage while other
compartments have not yet become involved.
 Hot gases and flames extending from the involved compartment transfer heat to
other fuel packages (e.g., contents, compartment linings, and structural materials)
resulting in fire spread. Conditions can vary widely with a fully developed fire in
one compartment, a growth stage fire in another, and an incipient fire in yet another.
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Indicators of Fully Developed Stage.
 Building. As with the growth stage, size, construction, and fire load influence fire development.
 Fire effects on the building can change the ventilation profile
 Smoke. Smoke will darken to darker gray, brown, or black.
 Smoke color influenced to a substantial extent by what is burning, and color may vary.
 Volume, optical density, and volume of smoke will increase.
 The height of the hot gas layer and neutral plane at openings is influenced by the ventilation profile, but if the
compartment is not well ventilated, the hot gas layer will drop close to the floor as the fire progresses through this
stage.
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Indicators of Fully Developed Stage
 Air Track. Air track is dependent on the ventilation profile. However, given a single opening such as a door,
smoke will exit out the top while air moves in the bottom.
 A fully developed fire will generally develop a well-defined and strong air track.
 The velocity of smoke and air movement will commonly be quite high and smoke discharge will be turbulent.
 Heat. In this stage of fire development, the fire is producing substantial heat.
 There are likely to be visual indicators of high temperature such as blackened windows, crazing window glazing.
Hot surfaces (i.e., doors) may be detected using a fire stream or thermal imager.
 In addition high temperature can be felt, even when wearing structural firefighting clothing.
 Flame. Flames may be visible from the exterior, with extent indicating the area and extent of involvement to some
degree.
 Fire will involve the entire compartment in this post flashover stage of fire development.
 Flames may be readily visible, but also may be obscured by smoke, as the fire becomes ventilation controlled.
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Decay stage
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 A compartment fire may enter the decay stage as the available fuel is consumed or due to
limited oxygen.
 On a larger scale, without intervention an entire structure may reach full involvement and as
fuel is consumed move into the decay stage.
 The fire may also move to decay stage when the ventilation profile of the compartment or
building does not provide sufficient oxygen,
 Heat release rate decreases as oxygen concentration drops, however, temperature may
continue to rise for some time.
 This presents a significant threat as the involved compartment(s) may contain a high
concentration of hot, pyrolized fuel, and flammable gaseous products of combustion.

Behaviour of ventilated controlled fires
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 Under ventilation-controlled conditions excess pyrolite and flammable
products of combustion present in smoke are a significant hazard to
firefighters.
 While fuel, heat, and oxygen are present in proportion to support combustion
where the fire is burning, the heat of the fire is pyrolyzing more fuel vapor
than the fire can consume.
 In addition, incomplete combustion results in production of flammable gases
such as carbon monoxide.
 The speed of fire development is limited by the availability of atmospheric
oxygen provided by the current ventilation profile of the compartment or
building.

Behaviour of ventilated controlled fires
 in a ventilation-controlled state, any increase in the supply of oxygen to the fire will result in
an increase in heat release rate.
 Increase in ventilation may result from firefighters making entry into the building (the
access point is a ventilation opening), tactical ventilation (performed by firefighters), or
unplanned ventilation (e.g., failure of window glazing due to elevated temperature).
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Behaviour of ventilated controlled fire
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Ventilation Induced Extreme Fire Behavior
 When the fire is ventilation controlled, increased air supply to the fire will result in increased
heat release rate and depending on conditions may result in extreme fire behavior such as
flashover or backdraft.
 While similar, vent induced flashover and backdraft are different phenomena.
 When the fire is ventilation controlled and fuel gas and vapor in the smoke is below its
ignition temperature, increased ventilation is likely to result in a vent induced flashover.
 If fuel gas and vapor in the smoke is above its ignition temperature and the rate of
combustion is generally much faster (deflagration) producing a more violent backdraft
 Firefighters entering a compartment or building containing an under ventilated fire must be
aware of and manage the hazards presented by the potential for rapid-fire progress.
Remember, many if not most fires that have progressed beyond the incipient stage before
firefighters arrival are ventilation controlled and present the potential for rapid fire
progress with increased ventilation
31

Vent induced flashover Schematic diagram
32

Vent induced backdraft
33

Ventilation controlled decay
 The hazard of ventilation induced extreme fire behavior is increased when building contents have a high heat of
combustion.
 Smoke. Volume and optical density of smoke will increase.
 Under ventilation, controlled decay conditions the hot gas layer will generally (but not always) fill the compartment with
pressurized smoke exiting small openings.
 Smoke color influenced to a substantial extent by what is burning and color may vary.
 Light color smoke or black smoke becoming dense gray yellow. Yellow smoke is often associated with decay due to limited
ventilation (and backdraft conditions). However, color alone is not a reliable indicator as smoke may also be gray, black, or
brown.
 Smoke that is optically dense and has the appearance of texture is a more significant indicator. Raising and lowering of the
neutral plane (this is similar to pulsing air track, but in this case the compartment is not full).
 The height of the hot gas layer and neutral plane at openings is influenced by the ventilation profile, but if the compartment
is not well ventilated, the hot gas layer will drop close to the floor as the fire progresses through this stage
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Ventilation controlled decay Cont.
35
 Air Track. Air track in decay is dependent on the cause (lack of fuel or lack of oxygen). If due to a lack of oxygen, there
may be a pulsing air track (in and out or up and down) and the velocity of smoke discharge can be quite high with
significant turbulence. However, it is important to note that air track is significantly influenced by opening size and
proximity to the fire.
 Heat. Temperature during the decay stage can initially be quite high (and continue to rise for some time). There may be
visual indicators such as blackened windows, high velocity smoke discharge, and surfaces such as windows and doors are
likely to be quite hot. However, if decay is due to ventilation-controlled conditions, temperature will eventually drop (if the
compartment remains sealed).
 Flame .In ventilation-controlled decay flaming combustion is reduced.
 Flames may be present.
 Ignition of fire gases escaping from the compartment (as they mix with air) can provide a strong indication of fuel rich,
oxygen deficient decay conditions.
 Also, remember that conditions can vary considerably in different parts of the structure.
 Backdraft conditions can exist in a void space while you can see a fully developed fire with flames showing from several
windows.

explosives
 Explosives are chemical substances that deflagrates (burning rapidly than ordinary
fuel) and detonates (sudden ignition/explosion) on application of heat, shock,
friction or pressure (Kent, 2004).
 Upon deflagration or detonations, explosives are converted in a very short interval of
time into more stable gaseous substances through explosion. In explosion, a
considerable amount violent heat wave is generated that has a blasting, shattering or
brisance
 The energy released has four basic effects: rock fragmentation, rock displacement,
ground vibration and air blast (Brehm, 2011). Explosives may be classified as:
military explosives and commercial explosives, primary and secondary explosives,
homemade explosives and improvised explosives or in a class: A, B and C (Zeek,
1971; Oxley, 1998).
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Low & High explosives
 This is based on the rate of burning:
 Low explosives burn rapidly (or deflagrate) and High explosives ordinarily deton-
ate.
 There is no sharp line of demarcation between low and high explosives.
 The term "detonation" is used to describe an explosive phenomenon of almost
instantaneous decomposition. The properties of the explosive indicate the class into
which it falls. In some cases explosives may be made to fall into either class by the
conditions under which they are initiated. For convenience, low and high explosives
may be differentiated in the following manner.
 Low Explosives: These are normally employed as propellants. They undergo
autocombustion at rates that vary from a few centimeters per second to
approximately 400 meters per second. Included in this group are smokeless powders,
and pyrotechnics such as flares and illumination devices.
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High Explosives
 These are normally employed in warheads. They undergo detonation at rates of 1,000 to 8,500
meters per second. High explosives are conventionally subdivided into two classes and
differentiated by sensitivity: primary explosives and secondary explosives
 Primary. These are extremely sensitive to shock, friction, and heat. They will burn rapidly or
detonate if ignited.
 Secondary. These are relatively insensitive to shock, friction, and heat. They may burn when
ignited in small, unconfined quantities; detonation occurs otherwise.
38

Military and commercial explosives
 Classification is based on standardization and usage:
 Many explosives have been studied in past years to determine their suitability for
military use and most have been found wanting. The requirements of a military
explosive are stringent, and very few explosives display all of the characteristics
necessary to make them acceptable for military standardization. Some of the more
important characteristics are:
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Characteristics of military explosives
 Availability and Cost. In view of the enormous quantity demands of modern warfare, explosives must be produced from
cheap raw materials that are nonstrategic and available in great quantity. In addition, manufacturing operations must be
reasonably simple, cheap, and safe.
 Sensitivity. Regarding an explosive, this refers to the ease with which it can be ignited or detonated--i.e.,the amount and
intensity of shock, friction, or heat that is required
 Stability. Stability is the ability of an explosive to be stored without deterioration. The following factors affect the stability of
an explosive:
• (1) Chemical constitution--The very fact that some common chemical compounds can undergo explosion when heated
indicates that there is something unstable in their struc-tures..
• (2) Temperature of storage--The rate of decomposition of explosives increases at higher temperatures. All of the standard
military explosives may be considered to be of a high order of stability at temperatures of -10o to +35oC, but each has a high
temperature at which the rate of decom-position becomes rapidly accelerated and stability is re-duced. As a rule of thumb,
most explosives becomes danger-ously unstable at temperatures exceeding 70oC.
• (3) Exposure to sun--If exposed to the ultraviolet rays of the sun, many explosive compounds that contain ni-trogen groups will
rapidly decompose, affecting their sta-bility.
40

 Power. The term power (or more properly, performance) as it is applied to an explosive refers to its ability to do work. In
practice it is defined as its ability to accomplish what is intended in the way of energy delivery (i.e., fragments, air blast, high-
velocity jets, underwater bubble energy, etc.). In addition to strength, explosives display a second characteristic, which is their
shattering effect or brisance (from the French meaning to "break"), which is distinguished form their total work capacity.
 This characteristic is of practical importance in determining the effectiveness of an ex-plosion in fragmenting shells, bomb
casings, grenades, and the like. The rapidity with which an explosive reaches its peak pressure is a measure of its brisance.
 Density. Density of loading refers to the unit weight of an explosive per unit volume. Several methods of loading are available,
and the one used is determined by the characteristics of the explosive. The methods available include pellet loading, cast
loading, or press loading. Dependent upon the method employed, an average density of the loaded charge can be obtained that
is within 80-95% of the theoretical maximum density of the explosive. High load density can reduce sensitivity by making the
mass more resistant to internal friction. If density is increased to the extent that individual crystals are crushed, the explosive
will become more sensitive. Increased load density also permits the use of more explosive, thereby increasing the strength of
the warhead.
41

 Volatility. Volatility, or the readiness with which a substance vaporizes, is an undesirable characteristic in military explosives.
 Explosives must be no more than slightly volatile at the temperature at which they are loaded or at their highest storage
temperature.
 Excessive volatility often results in the development of pressure within rounds of ammunition and separation of mixtures into
their constituents. Stability, as mentioned before, is the ability of an explosive to stand up under storage conditions without
deteriorating.
 Volatility affects the chemical composition of the explosive such that a marked reduction in stability may occur, which results
in an increase in the danger of handling. Maximum allowable volatility is 2 ml. of gas evolved in 48 hours.
 Hygroscopicity. The introduction of moisture into an explosive is highly undesirable since it reduces the sensitivity, strength,
and velocity of detonation of the explosive. Hygroscopicity is used as a measure of a material's moisture-absorbing tenden-
cies. Moisture affects explosives adversely by acting as an inert material that absorbs heat when vaporized, and by acting as a
solvent medium that can cause undesired chemical reactions. Sensitivity, strength, and velocity of detonation are reduced by
inert materials that reduce the continuity of the explosive mass. When the moisture content evaporates during detonation,
cooling occurs, which reduces the temperature of reaction. Stability is also affected by the presence of moisture since moisture
promotes decomposition of the explosive and, in addition, causes corrosion of the explosive's metal container. For all of these
reasons, hygroscopicity must be negligible in military explosives.
 Toxicity. Due to their chemical structure, most explosives are toxic to some extent. Since the effect of toxicity may vary from
a mild headache to serious damage of internal organs, care must be taken to limit toxicity in military explosives to a minimum.
Any explosive of high toxicity is unacceptable for military use.
42

Commercial explosives
 Commercial explosives are widely used in agriculture, construction and mining as a form of
technology enhancement in these field (Johnson & Goldstein,1983).
 The categories of commercial explosives include dynamite and ammonium nitrate fuel oil (ANFO),
water gel, boosters, plastic explosives, binary explosives, slurry, shaped charges and emulsions
(Zhang, 2016).
 These explosive materials are commercially available for purchase. They are easily accessible to the
terrorist. The military and commercial explosives can also be classified based on their rate of
detonation or deflagration as high explosives and low explosives (Suceska, 1995). Accordingly, they
can also be classified as primary or secondary explosives based on their sensitivity to shock, heat and
friction (Mehta & Oyler, 2014)
43

Homemade explosives
 The home-made explosives are types of explosives made at home without specifications for their explosive chemical specifications.
 Instructions how to make them are available in the internet. The recipes for homemade explosives are often inaccurate and dangerous to
follow.
 These explosives are unstable, and they are made in clandestine locations.
 They include recipes for nitro-glycerine, mercury fulminate, blasting gelatine, dynamite, TNT, tetryl, picric acid and black powder. They are
widely used in making car bombs, pipe bombs and by suicide bombers.
 They are easily concealed in many ingenuity manner in items that presents themselves like: unusual devices or containers with electronic
components such as wires, circuit boards, cellular phones, antennas, and other items attached or exposed; devices containing quantities of
fuses, fireworks, matchheads, black powder, smokeless powder, incendiary materials and unusual materials or liquids. They are also enhanced
in materials attached to items such as nails, bolts, drill bits, marbles so that these items could also be used as shrapnel.
 They are also presented as ordinance items such as blasting caps, detonator cord (Detcord) military explosives, grenades or any combustible
materials (Vernon, n.d).
 The EDDs are specifically trained to detect the three classes of explosive materials used as active ingredients for making IEDs
44

Improvised explosive and improvised explosive device(s).
 Improvised explosives (IE) are explosives used in contravention to the manufactures
specification for other purpose that integrate the characteristics of explosives: detonation and
deflagration.
 These explosives are used to assemble/make improvised explosive devices (IEDs).
 and improvised explosive device is a device constructed in an improvised manner in respect
from its original intended function in terms of explosive ingredients, triggering or detonation
mechanism and delivery systems.
 The IEDs component may incorporate any or all military munitions, commercial explosives,
or homemade explosives.
 The components and device design vary in sophistication from simple to complex. IEDs can
be used by both state and non -state actors (UN, 2018).
45

IEDs Cont
 The IEDs consist of variety of components that includes: the initiator, the switch, the main charge, power source
and a container (Schubert & Kuznetsor, 2006; Homeland Security. N.d, Van – Raj, 2017).
 IEDs may be surrounded by or packed with additional materials or “enhancers” such as nails, glass, or metal
fragments designed to increase the lethality of the shrapnel’s’ propelled by the explosion. Enhancement may also
include other elements such as hazardous materials.
 Despite IEDs being viewed as rudimentary, simplistic and makeshift device that has been cobbled together with
little thought or attention, they are highly complex weapons with increasingly sophisticated components that are
difficult to detect (Small Arms Survey, 2014).
 They come in numerous different forms, often with multiple dimensions to their designs, are deployed in different
ways and places, and are designed to have different impacts (UN General Assembly, 2015).
 Studies have shown that civilians often bear the brunt of IEDs violence. In 2015, 85 % of casualties in civilians
was inflicted by the IEDs and was the highest killer of civilians in the first half of 2016; UN General Assembly,
2016). An IED can be initiated by a variety of modes depending on the intended target (Oxley, 1998, Gill et al,
2011; Revill, 2016)
46

Classification of explosives by class
• Class A, B and C explosives. The explosives are classified in this category based on the recommended mode of
transportation/hazards (Zeek, 1971).
 class A explosives are very a high hazardous potential and are shipped or carried on a rail and few special vehicles are
authorized to carry explosives in this class. The explosives included in this classification are: All initiating explosives including
PETN; high explosives, including RDX; dynamite; blasting caps and electric blasting caps that are more than 1000; shaped
charges and explosive bombs
 Class B explosives are carried by special arrangement mode of rail, water and air transportation. They have less hazard
potential than class A explosives. This category of explosives includes double base propellant with less than 20% nitro-
glycerine; canon and riffle powders and solid propellants.
 Class C have a lesser hazard potential than both class A and B and are easily transported by road, rail and air transport. The
type of explosives included in this category are: blasting caps and electric blasting 1000 or less; prima cord; percussion fuses;
combination fuses and time fuzes.
47

The scientific model of fire and explosive investigation
48
 This model seek to investigate the fire and explosives phenomenon in an analytical
approach in understanding, prediction and control of accidental and willful fire phenomena
 The scientific investigation process starts with a phenomenon that is not understood, and uses
observations, measurement, testing and logical reasoning to develop an ordered description of
or hypothesis about a phenomenon.
 To gain new understanding and control, the investigator needs to develop new knowledge,
order it and test it for validity.
 To be of value, the new knowledge must be in a usable form by any party needing to make the
predictions or achieve control.
 This can be achieved if the investigator produces a valid, tested and
comprehensive description of the fire, free of guesses and opinions about fire cause, and
readily acknowledging remaining uncertainties.

Methodology of fire investigation
49

Methodology of bomb & Explosives investigation
50

Approaches to fire and explosives investigation
51
 Investigative Tasks. Investigative tasks relate to the information gathering processes that feed into investigative thinking and the results. Investigative thinking, on
the other hand, is the process of analyzing information and theorizing to develop investigative plans.
 Investigative thinking is aimed at analyzing the information collected, developing theories of what happened, the way an event occurred, and establishing
reasonable grounds to believe. Those reasonable grounds to believe will identify suspects and lead to arrest and charges. Investigative thinking is the process of
analyzing evidence and information, considering alternate possibilities to establish the way an event occurred and to determine if they are reasonable
 The investigative process is a progression of activities or steps moving from evidence gathering tasks, to information analysis, to theory development and
validation, to forming reasonable ground to believe, and finally to the arrest and charge of a suspect. Knowing these steps can be helpful because criminal incidents
are dynamic and unpredictable. The order in which events take place, and the way evidence and information become available for collection, can be unpredictable.
Thus, only flexible general rules to structured responses can be applied. However, no matter how events unfold or when the evidence and information are received,
certain steps need to be followed. These include collection, analysis, theory development and validation, suspect identification and forming reasonable grounds,
and taking action to arrest, search, and lay charges.
 Mental Map. Mental map is an appropriate strategy to illustrate the investigative thinking process. In this process, even though the path to investigate may be
unclear and unpredictable at first, the destination, the results we seek in our investigation, will always be the same and can be expressed in terms of results and their
priorities. Results and priorities focus first on the protection of the lives and safety of people. They focus second on the priorities of protecting property, gathering
and preserving evidence, accurately documenting the event, and establishing reasonable grounds to identify and arrest offenders.

Investigative Response Priorities
A response that would sacrifice the safety of people to achieve a level two
priority would not be justifiable and could even lead to civil or criminal
outcomes against the investigators making such a choice.
 Level 1 : Tactical Responses. Tactical Investigative Response is faced by
operational officers who are engaged in the frontline response to criminal
events. Responders are often challenged to respond to events, sometimes life
and death situations, where information is limited and critical decisions need
to be made to act. In these Tactical Investigative Responses, the responding
officers often have little or no time to undertake the tasks of managing crime
scene appropriately. They must rely on the information of a dispatched
complaint, coupled with their own observations made once they arrive at the
scene. If an officer takes the action of making an arrest or using force to bring
the situation under control, they are accountable for the action they have
taken, and they may be called upon by the court to articulate their thinking,
albeit based on limited information.
 Level 2 : Strategic Responses. Once an investigator has arrived at the scene
of an event and has brought the event under control by either making an
arrest or by determining that the suspect has fled the scene and no longer
poses a threat to the life or safety of persons, the investigation becomes a
strategic investigative response. With this expiration of life and safety issues,
also comes the expiration of exigent circumstances and the additional
authorities to detain persons suspected and to enter and search private
property without a warrant.

Response Transition Matrix
Two of the most important situational elements to understand are event classification and offence recognition. For each of these classifications of active event or
inactive event, the investigator has some different legal authorities to put into action, as well as some immediate responsibilities for the protection, collection, and
preservation of evidence. When attending the scene of any reported event, the investigator should assume that the event is active until it has been established to be
inactive. The defining elements between active event and inactive event are. The defining elements between active event and inactive event are: The criminal act is or
may still be in progress at the scene.
 The suspect is or may still be at the scene of the event.
 The situation is, or may be, a danger to the life or safety of a person, including the life or safety of attending police officers.
 The criminal act has concluded at the scene.
 The suspect or suspects have left the scene or have been arrested or detained.
 The situation at the scene no longer represents a danger to the life or safety of a person, including police officers.

The RTM
 Errors of Strategic Investigations. The three most common
errors of the Strategic Investigative Response are:
 Failing to identify and collect all the available evidence and
information,
 Failing to effectively analyze the evidence and information
collected to identify suspects and form reasonable grounds to
take action, and
Becoming too quickly focused on one suspect or one theory of events
and ignoring evidence of other viable suspect or theories that should
be considered. There are many possible sources of additional
information and evidence to consider, such as:
• criminal records info, outstanding warrants and pointers to
criminal association
• information on past records of complaints, investigations of
criminal activities, and historical criminal associations
• ViCLAS (Violent Crime Linkage Analysis System) provides a
database of searchable criminal conduct acquired from the past
crimes of known offenders
MVB (Motor Vehicle Branch) records for current vehicles registered,
driving record, physical descriptors, and resident address

Thorough investigation and Investigation funnel
A thorough investigation is one with systems to:
• Identify and collect all available evidence,
• Identify all the witnesses, victims, and possible suspects,
• Accurately document the criminal event,
• Accurately document the investigative actions,
• Develop theories of how the crime was committed and who may be a suspect,
and
Formulate an investigative plan to form reasonable grounds and make an arrest

The Investigation Thinking template : STAIR Model
From the onset, the investigator is met with a situation
Situation that must be resolved. With this situation
understood, immediate Tasks must then be undertaken
to protect life and safety, gather relevant information,
preserve evidence, and identify offenders. Lastly, in
every situation, the information discovered must be
analyzed to inform and guide the Investigation that
must happen to reach the desired Results.

The mandatory tasks performed at the crime scene
Establishing the Integrity of Crime Scene
There are tasks that must be performed by the investigator
before commencing the process of identifying, collecting,
preserving, and protecting evidence to ensure that evidence
will be accepted by the court. These tasks include:
 Locking down the crime scene
 Setting up crime scene perimeters
 Establishing a path of contamination point in time,
and those activities could have Contaminated the
crime scene in various ways.
 Locking down the crime scene means that all
ongoing activities inside the crime scene must stop,
and everyone must leave the crime scene to a
location some distance from the crime scene area.
Once everyone has been removed from the crime
scene, a physical barrier, usually police tape, is placed
around the outside edges of the crime scene. Defining
of the edges of the crime scene with tape is known as
establishing a crime scene perimeter. This process of
isolating the crime scene inside a perimeter is known
as locking down the crime scene
Setting up crime scene perimeters
The crime scene perimeter defines the size of the crime scene, and it is up to the investigator to
decide how big the crime scene needs to be. The size of a crime scene is usually defined by the
area where the criminal acts have taken place. This includes all areas where the suspect has had
any interaction or activity within that scene, Including points of entry and points of exit. The
perimeter is also defined by areas where the interaction between the suspect and a victim took
place. In some cases, where there is extended interaction between a suspect and a victim over
time and that activity has happened over a distance or in several areas, the investigator may need
to Identify one large crime scene, or several smaller crime scene areas to set crime scene
perimeters.
Once the crime scene perimeter has been established and lock down has taken place, it becomes
necessary to ensure that no unauthorized persons cross that perimeter. Typically, and ideally, there
will only be one controlled access point to the crime scene, and that point will be at the entry
point for the path of contamination.
Establishing a path of contamination
Information being gathered will document what evidence has been moved, what evidence has been
handled, and by whom. With this information, the investigator can establish a baseline or status of
existing contamination in the crime scene. If something has been moved or handled in a manner
that has contaminated that item before the lock down, it may still be possible to get an acceptable
analysis of that item if the contamination can be explained and quantified.
With everyone now outside the crime scene and the perimeter locked down, the next step is to
establish a designated pathway where authorized personnel can re-enter the crime scene to
conduct their investigative duties. This pathway is known as a path of contamination and it is
established by the first investigator to re-enter the crime scene after it has been locked down.

Crime scene integrity
Establishing crime scene security
At the same time the crime scene is being defined with perimeter tape, it
is also necessary to establish a security system that will ensure that no
unauthorized person(s) enters the crime scene and causes contamination.
For this purpose, a crime scene security officer is assigned to regulate the
coming and going of persons from that crime scene. For the assigned
security officer, this becomes a dedicated duty of guarding the crime
scene and only allowing access to persons who have authorized
investigative duties inside the crime scene. These persons might include:
 Forensic specialists
 Search team members
 Assigned investigators, and/or
 The coroner in the case of a sudden death investigation
To maintain a record of everyone coming and going from the crime
scene, a document, known as a “Crime Scene Security Log”, is
established, and each authorized person is signed in as they enter and
signed out as they depart the scene with a short note stating the reason
for their entry. Any unauthorized person who enters or attempts to enter a
crime scene should be challenged by the crime scene security officer,
and, if that person refuses to leave, they can be arrested, removed from
the scene, and charged for obstructing a police officer.
Scaling the Investigation to the Event
Not every crime scene is a major event that requires an investigator to
call out a team and undertake the crime scene and evidence
management processes that have been described. Often, for minor
crimes, a single investigator will be alone at the crime scene and will
engage in all the roles described, albeit on a far smaller scale.
When this process is being undertaken by a single investigator on a
smaller scale, the issues of diagram, security log, and exhibit log may
be limited to data and illustrations in the notebook of the investigator. It
is important to stress that each of the tasks below needs to be
considered and addressed for every crime scene investigation, no
matter how big or how small. Specifically:
• The crime scene must be secured, preserved, and recorded until
evidence is collected
• Existing contamination must be considered and recorded
• Cross-contamination must be prevented
• Exhibits must be identified, preserved, collected, and secured to
preserve the chain of continuity. Large scale or small scale, all
these issues must be considered, addressed, and recorded to
satisfy the court that the crime scene and the evidence were
handled correctly.

Crime scene documentation: Photography, note taking & sketching
Crime Scene Photography
‘One picture is worth a thousand words’ saying certainly holds true with
crime scene photography. The purpose of crime scene photography is to:
• Record the original scene and related areas.
• Record the initial appearance of physical evidence.
• Provide investigators & others permanent visual record of the
scene.
• Provide a record to be utilised in court.
Photographs should be taken of all things of significance and should
accurately record the location of items within the scene.
The photographs should be taken before scene is examined and items are
not to be moved as this will provide a record of items and the scene in its
original state prior to police intervention.
The types of photographs taken should include:
• General photographs (exterior and interior) showing the
location of the scene.
• Mid-range photographs (again exterior and interior) to
record the positions of relevant items within the scene.
• Close-up photographs showing the item of interest in detail.
When photographing, an impression a scale should be placed within the
photograph.
Hand Written Notes
The crime scene examiner should take accurate and extensive notes. These
can include entries in police notebooks and within forms specifically designed
for crime scene recording. These notes need to be accurate and should include
the following:
• The time and date the call was received to attend the scene.
• The time, date and with whom you attended at the scene.
• The names of those you spoke to at the scene.
• Actions carried out at the scene including exhibits collected,
examinations carried out and conclusions reached.
Handwritten notes are important because they:
• Provide details permanent record of the investigation
• Enable the distribution of information to all investigators
• Enable the presentation of accurate information in court
• Assist to refresh your memory at a later time.

Sketches
Crime scene sketches clarify the appearance of the scene and
make it easier to comprehend.
Information to be Included in the Sketch:
The sketch should include at least the following information:
• The crime scene specialist‘s full name and
assignment.
• The date, time, crime classification, and report
number.
• The full name of any person who assists in taking
measurements.
• Address of the crime scene, its position in
building, landmarks, and compass direction.
• The scale of the drawing, if a scale drawing has
been made.
• The major discernible (perceptible), items of
physical evidence and the critical features of the crime scene.
The location of such items is indicated by accurate measurements
from at least two fixed points, or by other methods discussed
below.
• A legend or key to the symbols used to identify
objects or points of interest on the sketch.
Types of Crime Scene Sketches
 Rough Sketch. A rough sketch is drawn free hand by the crime scene specialist at the scene of
the crime. Changes should not be made to it after the specialist has left the scene. This sketch
will not normally be drawn to scale, but will indicate accurate distances, dimensions, and
relative proportions.
 Detailed Sketch. A smooth sketch is one that is finished and is frequently drawn to scale from
the information provided in the rough sketch. If a sketch is drawn to scale, the numbers
concerning the distances can be eliminated. However, if the sketch is not drawn to scale, the
distances need to be shown.
Methods of sketching
 Coordinate Method. The coordinate method measures the distance of an object from two fixed
points. One form of this method uses a baseline, which is drawn between two known points. The
baseline could be a wall, or drawn as a mathematical centre of a room, the exact dimensions of
which are known. The measurements of a given object are then taken from left to right along the
baseline, to a point at right angles to the object, which is to be plotted. The distance will be
indicated in the legend with a number in parentheses following the name of the object.
 Triangulation Method. The triangulation method is useful in an outdoor situation where there
are no easily identifiable edges of roads or fields to use as reference points. Two or more
reference points are located and should be widely separated if possible. The item of interest is
located by measuring along a straight line from the reference points.
 Cross-Projection Method. The cross-projection method is useful when the items or locations of
interest are on or in the wall surfaces as well as elsewhere in an enclosed space. The walls,
windows, and doors. The sketch is by projecting distances from these fixed positions

Crime Search
The search for physical evidence at crime scene must be thorough and systematic. Assigning those responsible for searching
a crime scene is a function of the investigator in charge. The crime scene search is conducted to uncover the physical
evidence that will potentially do the following:
• Determine the facts of the crime
• Identify the criminal
• Aid in the arrest and conviction of the criminal
During the crime scene search for physical evidence, special attention must be directed to the discovery and documentation
of impression evidence. Impression evidence is often not readily apparent, therefore, each of the areas of possible contact
between the perpetrator and the scene must be carefully examined with the full expectation that it will contain impression
evidence.
• Point of Observation. Perpetrators sometimes observe a scene from a distance prior to committing a crime, or
they may stalk a victim in preparation for an assault. Such vantage points, which offer the perpetrator a hidden viewpoint,
should be searched for shoe or tire impressions.
• Route to Scene .Take note of any contaminants (soil, dew, etc.). That may have collected on shoe soles along the
route used to approach a crime scene. These contaminants may be deposited at the point of entry and within the scene. Soft
outdoor surfaces along the approach route may contain impression evidence that can be collected and may allow for an
interpretation of the number of perpetrators by noting the number of different shoe sole patterns that are present.
•

Crime search Cont.
During the crime scene search for physical evidence, special attention must be directed to the discovery and documentation of impression evidence. Impression evidence is often not
readily apparent, therefore, each of the areas of possible contact between the perpetrator and the scene must be carefully examined with the full expectation that it will contain impression
evidence.
• Point of Observation. Perpetrators sometimes observe a scene from a distance prior to committing a crime, or they may stalk a victim in preparation for an assault. Such
vantage points, which offer the perpetrator a hidden viewpoint, should be searched for shoe or tire impressions.
• Route to Scene .Take note of any contaminants (soil, dew, etc.). That may have collected on shoe soles along the route used to approach a crime scene. These
contaminants may be deposited at the point of entry and within the scene. Soft outdoor surfaces along the approach route may contain impression evidence that can be collected and
may allow for an interpretation of the number of perpetrators by noting the number of different shoe sole patterns that are present.
• Point of Entry .The point of entry is often a likely location to recover impression evidence. Contaminants that have collected on the shoe soles are often deposited on
interior surfaces upon entry. Pay special attention to window sills, chair seats, desk and table tops at or near the point of entry. Additionally, forced entry may have been accomplished by
kicking in a door or climbing to access a window. These surfaces should be thoroughly searched for impression evidence.
• Route through the Crime Scene .A methodical visible search with existing light should be conducted anywhere that the route of the perpetrator is apparent or suggested.
Search for impressions in blood, grease, dust, etc. Take note and collect any objects that bear indentations that may have been caused by being stepped on by the perpetrator. Strewn or
dropped paper items (envelopes, magazines, boxes, etc.) should be recovered from floor surfaces to be examined for the presence of dust or residue impressions.
Following the search with existing light, a thorough search should be made using a bright floodlight held just off of the surface to direct a beam of oblique (low angle) lighting across the
surface. This should be done in darkened room conditions and may reveal dust or residue impressions that were not otherwise apparent.
• Point of Occurrence .This is the area in a crime scene that the focal point of the criminal activity is obvious. This may be an area where ransacking has taken place,
(going through stealing and destroying things) where a struggle with the victim has taken place, or where the victim‘s body is located. Impressions may be deposited in blood or other
body fluids or on objects that have been displaced or knocked over. In murder cases, the victim‘s body and clothing are a potential source of impressions.
• Point of Exit. Recover impressions from the area immediately adjacent to the point of exit. This includes impressions in soft exterior ground surfaces. Any surface that
may have been contacted during exit should be searched.
• Escape Route from the Scene .Attempt to reconstruct the direction and means of escape from the scene. Be alert for other evidence associated with pathways from the
scene such as discarded weapons and other property.

Crime Scene Search Methods
There are five (5) systematic search methods normally utilized to search crime scenes. They include the spiral search, strip search, grid search, zone or sector search,
and the pie or wheel search.
• Spiral Search Method .This ever-widening circle technique is conducted with the searching officer starting at the focal point of the crime scene or the
center of the area, working outward by circling in a clockwise or counter-clockwise direction to the outside edges of the crime scene. A spiral technique is a good
pattern for a rather confined area. This works well in a small room. In addition to using the spiral pattern in a room, it is also helpful to apply this pattern in layers.
This can be done as follows:
• Visually search the top third of the rooms, as well as the ceiling. Police officers typically do not look up very often, but should in the case of a crime
scene. There may be bullet holes in the ceiling, blood splatter or hidden items.
• Search the middle third of the room including drawers and cabinets.
• Search the lower third, using the spiral technique. The floor and lower cabinets are typically where most evidence is located.
• Grid search. (Pattern of lines forming squares) The grid search is a variation of the strip search and is useful for large crime scenes, particularly
outdoor scenes. After completing the strip search, the searchers are doubled back perpendicularly across the area they just searched. It is very time consuming, but
causes a very methodical and thorough examination of the area. It also has the advantage of allowing searchers to view and search the crime scene from two different
viewpoints, thereby increasing the possibility of uncovering evidence not previously noticed.
• Strip Search .A strip search is typically used in outdoor scenes to cover large areas in which detailed examination is necessary. It is a technique
frequently used to search a particular area. The strip search uses a series of lanes across the crime scene. This method can be used by one person or a group of
searchers. It is done as follows:
• Each lane contains a searcher that walks down the lane parallel to the other searchers.
• Once the searchers get to the end of the lane they reverse their direction and walk back adjacent to the lane they just searched.
• This process is continued until the entire crime scene area has been searched.
• If one of the searchers finds evidence, all searchers should stop until the evidence is properly processed and they receive additional information.
• Zone or sector search .A zone or sector search is used when the search area is particularly large and cumbersome. The zone or sector search requires
the crime scene to be divided into four large quadrants (the four large quadrants can also be sub-divided into four smaller quadrants). Each quadrant or sector is then
searched separately as an individual unit, using the spiral, strip and/or grid search pattern.
• Pie or Wheel Search .The pie or wheel search is based on the establishment of a circle surrounding the crime scene. The circle is then divided into six
quadrants in a pie-like fashion.
Combination Methods
It should be noted that a combination of search patterns can be applied if the circumstances of the scene demand it. The search should also be multi-dimensional
meaning that the examiners need to look in all directions including up and down.

The olfaction model of detecting fire fuel accelerants and explosive chemical substances
 K-9s: Refers to all category of trained dogs widely employed by military
and the police in security operations(Tracking dogs, cadaver dogs,
narcotics, guard dogs, attack dogs, and other detector dogs (Headquarters
, Department of Army, 1960, and 2005; Philips, 1971; Furton, 2010;
Ensiminger, 2011)
 Explosive Detection Dogs (EDDs). Dogs specifically trained to screen for
fire accelerants and explosives in security operations.
Goal of EDDs training: To create a dog that is efficient (able to screen
for explosives and accelerants ) and effective (able to produce intended
results) in screening (investigate methodically)for explosives and
accelerants substances and obedient (respond to commands) in a working
scenario/crime scene (Weider,1980, Shults,2002; Binders, 2002;
Rosenthal, 1997; Russel, 2001; Weisbord and Kachanoff, 2000; Oxely and
Waggoner, 2009). 64

Odour and scent concepts
Biotic species and abiotic substances naturally emit biotic volatile organic
compounds (BVOCs) and inorganic substances emits abiotic inorganic volatile
compounds (AVICs)
 They present themselves in form of odour or scent when perceived by
sensory organs (Schnitzer, 2010; Armengol,2015).
 The volatile chemical compounds (VCCs) deals with detrimental and desirable
environmental conditions and the related stress (Holopainen and Gershenzon,
2010)
Odour/scent dispersal. Scent and odour are dispensed from the source in a
cone shaped pattern following the path of least resistance or the direction of the
wind (Syrotuck,1972).
 The EDDs demonstrate three types of responses towards the generalized scent
or odour rafts: air scenting dogs’ behaviour; trailing scent behaviour and
tracking behaviour (Bryson, 1984; Johnson,1977).

The EDDs behavioural responses on scent rafts
Air scenting dogs: Follow the odour trail with their head up in the air and are
following the air scent rafts emanating directly from the source and being carried by
the air currents.
Trailing dogs :follow the trail with their head up when moving into the wind and
head down when following the trail in the same direction as the wind.
They often do not follow directly on the path of the scent rafts, and they may overrun
the scent track before turning.
They follow the scent rafts deposited on the ground surface.
Tracking dogs: follow the trail with their head down and noses on the scent path. It
is assumed that the tracking dogs follow scent deposited on the ground and may be
detecting contact or airborne scent.
However, Bryson et al, 1984 and Johnson, 1977 suggests that these behaviours are
based on observing the EDDs in a working scenario and there is little evidence to
confirm or deny these observations in determining the cues dogs employ.

Part 7:The EDDs Epistemology characteristics
 EDDs epistemology characteristics: The learning demonstrated by the dogs’
after training
 The EDDs training: techniques used to ensure that the behavioral responses
demonstrated by the EDDs are predictable (Mills,2005; IAABC Foundation,
2020) .
The EDDs Learning: the potentials for demonstrating behavioral responses in
their performance after the dog undergoes the necessary training required to be
able to screen for explosives (New Jersey Law Enforcement, NJLE; 2002;
Friend Animal Society, 2011; Headquarters, Department of the Army, 1960).

Dogs learning skills
Ability to communicate. Dogs are able to engage amongst themselves in a
meaningful communication amongst themselves and also with human
(Siniscalchi et al 2018)
 Communication: The ability to transmit meaningful information amongst
the dogs (conspecific communication) and with human (heterospecific
communication)
 Models of conspecific and heterospecific communication: visual
communication; acoustic communication; olfactory communication and
tactile communication (Siniscalchi, et al, 2018).
 Errors in EDD Performance. Most of the errors in EDDs training and
learning are contributed by mis -communication and mis -understanding in
heterospecific communication (Podbeinrsek and Serpell, 1997; Voith et al,
1992

The EDDs conspecific and heterospecific visual communication
Conspecific visual communication occurs when dogs’ display a wide range of
postures that signals their inner state and intentions to other dogs’
 heterospecific communication occurs between a dog and its caregiver or
handler (Handelman, 2012).
 Requirements for successful Communication. These two types of
communication successfully occur when both the dog and its caregiver or
handler are in proximity (Wells, 2017). Both conspecific and heterospecific
communication occurs when the dog demonstrates visual, olfaction, acoustic or
tactile behaviours (Siniscalchi, 2018)

Visual Conspecific Communication
 Dogs’ expressions. Dogs employ signals indicated by modifications of their
body parts: the body sizes, tail, facial region and mouth region muscles
(Bradshaw and Rooney, 2016; Handelman, 2012, Siniscalchi, 2018).
The modification: facilitated by voluntary and involuntary control of their
muscles.
 The increase of the dog’s trunk displays their confidence, alertness or threat
(Handelman, 2012).
 In increasing their body, the dogs’ pull themselves up to their full height, and
increasing the tension of the body muscles.
 The dogs’body size can also be increased by piloerection of their hackles.
 The tail is held high to communicate confidence, arousal or the dog’s willingness
to positively approach another dog or a person, while the tail is held stiff to
express a threat or the dog’s anxiety

Visual Conspecific communication
Tail .The tail is also held low or tucked between the limb to signal dog’s fear,
anxiety or appeasement.
They also wag their tails loosely from side to side to communicate
friendliness or excitability.
Facial expression. The dogs communicate about their inner state by
modifying; their facial expression, modifying their gaze, ears and mouth
position.
Eyes. Dogs stare at their opponents to threaten them and avoid making
eye contact to their opponents to appease them.
In agonistic situations, dogs’ open their eyes wide.

Dog training and learning
 Dog Training. The action of instructing the dog on skills of sniffing for explosives
and behavioural responses associated with the indication of the targeted scent (S+)
(IAABC Foundation, 2020)
EDDs Training methods describes the techniques used to ensure that the
behavioral responses demonstrated by the EDDs in their performance are
predictable (Mills,2005).
 The EDDs Learning refers to the potentials for demonstrating
behavioral responses in a working scenario (Furton,2010)
72

Dog training models
Training: is established through conventional behaviourist training techniques ( EDDs Mental
training and reinforcement) and is reinforced by experiential learning (Learning through
experience and reflection on doing) (McConnel,2016; Kolb and Kolb; 2019)’.
The EDDs specialty training. Habituation, classical conditioning, instrumental/operant
conditioning, and extinction of operant (Sanders; 2006).
specialty training: A combination of three divergent elements in some form of acceptable
equilibrium: the requirement of the dog to demonstrate an aggressive behaviour for canid
ancestry; instilling a predictable and machine-like obedience to command and an inbuilt
interpersonal bond with the handler with attributes of being loyal, predictable and
trustworthiness (Sanders,2006)
 Target scent: Specific or a combination of known chemical smell as perceived by the dogs
olfaction (Kim, 2014)
 The dog is trained to detect and locate for scent (Specific odour or known smell and its
chemical properties ) (Kim. 2014)
73

EDD Training cont.
 Training: is established through conventional behaviourist training techniques ( EDDs Mental training and
reinforcement) and is reinforced by experiential learning (Learning through experience and reflection on doing)
(McConnel,2016; Kolb and Kolb; 2019)’.
The EDDs specialty training. Habituation, classical conditioning, instrumental/operant conditioning, and extinction
of operant (Sanders; 2006).
 specialty training: A combination of three divergent elements in some form of acceptable equilibrium: the
requirement of the dog to demonstrate an aggressive behaviour for canid ancestry; instilling a predictable and
machine-like obedience to command and an inbuilt interpersonal bond with the handler with attributes of being
loyal, predictable and trustworthiness (Sanders,2006)
 Target scent: Specific or a combination of known chemical smell as perceived by the dogs olfaction (Kim,
2014)
 The dog is trained to detect and locate for scent (Specific odour or known smell and its chemical properties )
(Kim. 2014)
74

Models of EDDs training
EDDs training models. Four types of conditioning: habituation, classical,
instrumental/operant and extinction of operant conditioning (Hilliard, 2003,
Schmid, et al, 2015).
 Conditioning: Training the dog to behave in a certain way in certain circumstances
(IAABC, 2020)
Classical Conditioning: Classical involves learning of emotional and
reflexive responses through the formation of mental association between
stimuli (Hilliard, 2003). Michael, (2017),
Introduced by Ian Pavlov (Cambiaghi & Sachetti, 2005)
involves learning new behaviours through the process of associating two
stimuli to produce a new response in animals (Mcleod, 2014).
 Three stages involved: Before conditioning, during conditioning and after
conditioning.
75

Three stages of classical conditioning
 Stage 1: Before conditioning. Behaviours or responses in the dogs
occurs naturally or by instinct in response to environmental stimulation
(I.E no new behaviour has been learnt). (Hilliard, 2003; Michael, 2017),
 This behaviour occurring naturally is known as “unconditional response
(UR) and is triggered by unconditional stimuli (US)
This stage has also other stimuli that does not illicit any response to the
called neutral stimuli (NS),
Stage 2 :In this stage, the ‘NS’ is paired together with the ‘US’ to produce
a conditional stimuli (CS).
 Third Stage. The ‘CS’is associated with ‘US’to create a new response
called conditional response (CR).

Instrumental / Operant conditioning
 The process of learning through which the dog’s behaviour is changed by the
consequences, or result of that behaviour (Gonzalez and Sawicka,2014).
The four elements involved in an instrumental conditioning procedure: voluntary
response on the part of the dog; the consequence; response rule and the cue.
 The consequence in instrumental conditioning procedures are reinforcement and
punishment.
Many rewards and punishments are biologically powerful stimuli and are called
primary reinforcers or primary punishers
Dogs responds readily and strongly to these stimuli without having to be taught to
do so
some rewards and punishment called secondary reinforcers and secondary
punishers have little effects on a dog behaviour until they have been associated with
primary reinforcers or punishers” (Hilliard, 2003 pg 30)
Mcleod,2018; Law Enforcement Canine programme, 1993;Cherry &
Susman,2020; Starmark, 2015).

Extinction of conditioned operant
 Refers to the gradual decrease in response to a conditioned operant that occurs when
the stimulus is presented without reinforcers (Hartley and Phelps, 2012).
 The phenomena of extinction take place when CO, previously paired with an
unconditioned operant (UO), is presented in the absence of that CO, producing a
reduction in the conditioned response observed (Alvarez et al, 2014).
78

EDDs training on explosives sniffing
 Three courses required: mandatory groups of explosives training; the mission specific threat training and the home -made
explosives (HMEs).
 The specific types of explosives training: Includes specialized training in detecting explosives containing the following
chemical substances : RDX; PETN (PETN based Detcord); TNT, (Military TNT; Dynamite, (containing EGDN and NG); black
powder; (free flowing, time fuse, or safety fuse, or double base smokeless powder).
 The mission specific threat specialized training: Detection of the following types of chemical substabce: ammonium nitrate
(prilled or powder, or solid components of binary explosives; blackpowdwer substitutes (pyrodex and triple seven); blasting
agent; cast boosters; composition B; emulsions; nitromethane , photoflash/fireworks / pyrotechnic powders; plastic explosives
(unmarked and marked with detection agent), Semtex, single based smokeless powder, slurries tetryl and water gel.
 The homemade explosives specialized training : To include training on detection of : chlorate based mixtures (potassium
chlorate); nitrate based mixtures (Anfo nitrate); perchlorate based mixtures (potassium chlorate); urea nitrate and peroxide
based mixtures and to extreme instability of the peroxide based explosive compounds, training must be supervised by a
qualified explosive canine trainer; Hexamethylene Triperoxide diamine ( HMTD); Tricetone triperoxide (TATP) and a range of
new emerging threat based on liquid explosives.

Indications likely to be demonstrated by the EDDs in a working scenario
 Four types of indications: a ‘hit’; a miss; false alarm and correct rejection (GICHD,
2011).
 A hit is defined as an indication response in the presence of a positive sample odour.
A miss is a failure to emit an indication in response of a positive odour (S+).
A false alarm is incorrect indication in the presence of the negative odour (S -)
while a correct rejection is the correct withholding of an indication in the presence of
negative scent (S-).
Environment factors such as wind speed and direction, time of the day, precipitation and
ambient temperatures affect the scent dispersal patterns and the EDDs odour detection
efficacy (Gazit, 2003, Gazit, 2005, Concha et al 2014).

Usefulness of K-9s
• A well-trained canine detection team is the current “gold standard”
for locating samples at the fire scene that may test positive for
ignitable liquid residues (ILRs) in the fire debris analysis laboratory.
Canines are advantageous because they provide immediate feedback
and are mobile, allowing them to search a large space in a very short
time. However, canine alerts should not be relied upon unless
confirmed by laboratory analysis (pp. 18, 30). Many substances are
produced during a fire, but investigators are currently in a position to
look only for evidence of ignitable liquids, for which there is currently
validated instrumentation. Other chemical markers are of little value,
because there is no way to determine when they may have been
created during a fire (p. 23).

Fire debris analysis
• Fire debris analysis begins at the fire scene where a fire investigator
determines the point of origin. Fire debris is collected from the point of
origin then sent to the laboratory to determine whether the fire debris
contains ignitable liquid residues. Timely collection and preservation of fire
debris evidence is crucial due to the volatile nature of the ignitable liquid
residues. The presence of an ignitable liquid is a key factor in the
determining the cause of a fire as incendiary.
• Fire debris is a general term used to define the debris from a fire that is
collected as evidence for laboratory examination.
• The debris needs to be packaged in special containers that are sealed to
prevent vapors of flammable or combustible liquids from escaping

Causes of fire
The cause of a fire is determined by identifying the circumstances and factors which
were necessary for the fire to occur.
Those circumstances and factors include the device or equipment involved in the
ignition, the ignition source, the material first ignited, and the circumstances or actions
that brought all of these factors together allowing the fire to occur.
The cause of the fire is classified as natural, accidental, undetermined, or incendiary.
Classifying a fire assists in assigning responsibility and culpability.
Natural fires are considered acts of God, such as lighting, earthquakes, and wind.
Accidental fires are those where the proven cause doesn’t involve the deliberate or
intentional action of a human to ignite or spread the fire.
Undetermined 5 fires are those where the cause can not be proven or is unknown.
 Incendiary fires are those fires proven to be deliberately or intentionally ignited.,

Samples collection
 If an incendiary fire is suspected, the fire investigator collects samples from potential points of origin as evidence.
 The evidence most frequently collected is fire debris and other materials such as flooring, carpet, baseboard, and pieces
of furnishings.
 These samples of fire debris are suspected of containing ignitable liquid residues.
 The ignitable liquid residues are what remain of an ignitable liquid which is considered a possible source of ignition.
 The presence or absence of an ignitable liquid provides the fire investigator with information about one of the factors
evaluated in the cause of the fire.
 Fire debris evidence is collected into airtight containers to preserve the volatile ignitable liquid residues.
 The most common types of containers are metal cans, glass jars and polymer bags as shown below.
 There are differing opinions as to which container type is best. The presence of an ignitable liquid alone does not classify
the fire as incendiary other factors and circumstances must also be identified to come to that conclusion

Extraction of ignitable liquids from debris
Steam Distillation is a separation process for temperature
sensitive substances. The technique involves introducing the fire
debris into a container with an appropriate amount of water and
boiling. The vapors produces are condensed in the distillation
apparatus. Petroleum distillate residues float on top of a column of
water and are collected as visible liquids.

Ignitable liquids detection methods
Ignitable liquids are petroleum-based liquids that are either flammable or combustible.
Ignitable liquids are complex mixtures of hydrocarbons containing normal, branched, and
cyclic alkanes as well as aromatics and polynuclear aromatics. An example is gasoline
which is composed of over 400 compounds. These petroleum-based liquids are isolated
from crude oil by a variety of chemical processes.
 The best methods for fire debris detection include gas chromatography, which separates
the hydrocarbons within in the ignitable liquid residues before detection.
There are many detectors which may be used with the gas chromatograph. The choice of
detector depends on the amount of chemical information or sensitivity required in the
analytical method.
 These methods of detection include:
 gas chromatography,
 gas chromatography-mass spectrometry (GC-MS),
 two-dimensional gas chromatography - mass spectrometry (GC-GC-MS) and
 gas chromatography – mass spectrometry - mass spectrometry (GC-MS-MS).

Gas chromatography
 Gas chromatography is the basis for the detection of ignitable liquid residues. An analyte is injected into a heated port to be
vaporized, then is carried through a column by an inert gas such as helium. The column consists of a liquid phase immobilized
on the surface of an inert solid where the analyte is partitioned between the mobile phase (inert carrier gas) and the
stationary phase (liquid phase). Chromatographic columns are housed in an oven in which the temperature is controlled.
Columns vary in length, internal diameter, type and thickness of liquid phase. Injector temperatures, columns, gas flow rates,
and oven temperatures are modified to achieve separation of the analyte compounds from one another before detection.
 Common detectors of a gas chromatograph are flame ionization, thermal conductivity, electron capture detectors, and mass
spectrometers.
 Data is presented as a chromatogram, a plot of retention time versus intensity which contains peaks corresponding to the
separated compounds from the analyte.
 Gas chromatography is a natural match for ignitable liquid detection because of its capability to separate the complex mixture
into its major components. Advances in chromatography such as capillary columns provided additional data for interpretation
since better separation of the components was possible.
 Gas chromatography led to pattern recognition techniques for interpretation of the data and enabled an analyst to classify
ignitable liquids into groups based on their physical properties.

References
Gowlett , J. (2016). The discovery of fire by humans: a long & convoluted process
https://core.ac.uk/download/pdf/80779283.pdf
Keely, J. (2009). A Burning Story: The Role of Fire in the History of Life: Retrieved from:
file:///C:/Users/user/Downloads/K2009_Pausas_BurningStory%20(1).pdf4
U.S Department of Justice (2000). Fire & Arson Evidence. Retrieved from: https://
www.ojp.gov/pdffiles1/nij/181584.pdf
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