2. Trace Evidence

3. Contact Trace evidence may be
defined as
• Any material which, when left behind at scene
or, on the body of victim or assailant or, any
other thing that acts as clue and can be
presented in the court as an evidence.
• THE TRACE EVIDENCE HELPS IDENTIFICATION
OBJECTIVELY

4. • It helps in the recognition of the
evidence and its association with a
particular:
• Person
• Thing
• Place
• and acts as a clue for the identity
of that source.

5. • Trace Evidence is based upon the
principal known as,
Locard’s Exchange Principal

6. • Sir Edmond Locard
( 1877 – 1966 )
gave two principals,
1. Every contact leaves a
trace
2. Exchange of trace is usually
a two way process.

7. • Classical examples of the trace
evidence is a cases of:
Sexual Assault
PHYSICAL ASSAULT

8. SEXUAL ASSAULT
• In which transfer of biological material
such as semen, blood, saliva, hair
etc. occurs from:
• Assailant to Victim
• Victim to Assailant
• From Assailant & Victim both to the
scene of crime
• Non Biological Material from the
scene of crime to both Assailant and
the Victim.

9. LOCUS
ASSAILANT VICTIM

10. Objectives of Study
• 1- Identification of unknown
• 2- Confirmation of a previously known identity
• An attempt is made to establish similarity or
dis-similarity between two or more objects one
of which has come from a known source.
• Comparing this trace with a control taken from
the source from where it is suspected to have
come, will confirm the character of a trace and
its association is established.

11. • CLASSIFICATION
• Trace evidence may be grouped
into:
• 1. Biological Evidence
• 2. Non-Biological Evidence

12. Biological Evidence
These originates from
human, animal or plant source
and include mainly :
1. Body Fluids
2. Body Tissues
3. Stains

13. Body fluids
• Includes blood, semen, saliva,
urine, vomit, cerebro-spinal fluid,
etc.
• Such fluids may be found in the
form of stains at the scene,
clothes, and body of victim or
assailant.

14. • Other Biological materials
• Human Hair from head and
pubes.
• Scrapings from the under surface
of Nails which contains,
• Epithelium of skin of assailant or
victim deposited during physical
or sexual assault.

15. Non-Biological Evidence
• These comprises of
1. Items of Personal Use
2. Other Materials found in the
Environment (Foreign Bodies)

16. • These Personal Items are Clothes,
Spectacles, Purse, Wristwatches, or
other things in use.
• The Environmental Materials are fibres
from carpet, vegetation in the garden, grit
particles from the road.
• Other Non-Biological materials consists
of bottles, tablets, bullets or pellets,
weapons of offence or any other thing
used in the crime.

17. Collection,
Preservation, &
Dispatch
of Specimen
(Trace Evidence)
To
Analytical Laboratory

18. • The scientific study of the specimens
pre-requires:
1. Collection of Material from source
2. Its Preservation
3. Despatch to the laboratory

19. The procedures involved in Medico-Legal
cases are different from those involved in
the clinical labs and requires special
knowledge.
• WHY ?
• 1. The place of collection / sampling
• 2. Interest of parties involved
• 3. Safety against tampering
• 4. Chain of custody

20. • The study of trace evidence FOR THE
PURPOSE OF UNDERSTANDING is
divided into:
1. Pre-Lab work
2. Lab Work

21. • Pre-Lab Work is further divided
into,
a) General Instructions, which
are applicable to all specimens,
and
b) Special Instructions, which
are specific instructions for each
specimens.

22. Pre-Lab Work
A) General Instructions

23. 1. Consent For Collection
• Authority :
• Request for collection is made by Police or
Magistrate in writing.
• Written Consent of the person with
signature or thumb impression. If the
persons refuses to give consent, then note
it down and send the person back to
authority.

24. 2. Identification Of Person
• Identification is important in both
living or dead, which is done by,
• a) Subjective
• b) Objective
• c) Third Party
• Two identification marks are noted.

25. 3. Collection of Specimens
• The person must have the knowledge as
to :
a) What is to be collected (source)
b) From where to be collected (site)
c) How much to be collected (quantity)
d) How it is to be collected (procedure)
A proper material from a proper site in a proper
quantity by a proper method.
(proper collection)

26. 4. Collection of Specimens
To ensure that the collection is proper, it
is advised that the process of collection
should be divided into various stages
and each phase has its own limited
goals.
These phases are
Overview Phase
Detailed discovery Search phase
Recovery Phase
Review Phase

27. 1- Overview Phase
In this phase the examiner should go
through the history of the case, study
the documents and visit the scene of
crime and should have an overall
view of the scene of crime, position
of body, location of objects, etc.

28. 2- Detailed discovery Search phase
In this phase the examiner should
concentrate on the areas of interest
and should search for the evidence
by walking through the area from end
to end twice, move the things, move
the body to look underneath body
etc.

29. 3- Recovery Phase
Specimens are collected and each item
should be identified, noted for its location
and if possible be photographed.
4- Review Phase
In this phase go through all the above three
phases and ensure that nothing is left,
because if left then it will be left for ever
and you may miss some important
evidence.

30. • The specimen may be present in
three forms,
.Dry form
.Wet Form
.Mixed with other
Articles.

31. Dry Form
– Scrap the specimen and place in a funnel of
glazed paper, or
– soak the cotton swab in normal saline and
apply it over the dry stain, then dry this
swab in air and use this swab as specimen.
Wet Form
-Dry the specimen and then scrap it or wipe it
with wet cotton swab.
Mixed Form
-Cut that portion and separate it

32. PACKING
• The Material of the Container should be
appropriate, Which means it should be
chemically inert, generally a Glass container
is recommended. But as glass being fragile,
plastic containers with lid are also used.
• The Size and Shape of the Container should
be appropriate, so that material should be
easily placed in it.
• A proper container, of proper material and
proper size (proper packing)

33. 5. Preservation
• The preservation of specimens is done
normally by two processes,
• Desication or Dehydration
• Freezing
• A proper preservative, in proper quantity
having proper concentration.
(proper preservation)

34. Preservation in Different Situations
• In Histo-pathological examinations we need a
preservative which should preserve & prevent
autolysis and harden the tissues.
• For Chemical examinations we only require
preservation.
• For Serological Examinations we also need
anti-coagulative activity.

35. A GOOD PRESERVATIVE
• It should be Cheap
• It should be Easily Available
• It should be also Chemically Inert
• It should be Effective for the purpose
• It should not react with the container &
specimen

36. Normally used Preservatives are,
• For Chemical Analysis, Super-Saturated Saline
is used. It acts by de-hydration ie; extracts water
from the tissues & they get preserved.
• For Histo-pathological Examinations 10%
Formal Saline ( ie; 10% folmalin in saturated
saline) or 95% Alcohol is used.
• For Serological Examinations anti-coagulants
used are, Ca. Oxalate, Heparin, etc;

37. Type Of Material Size & Lids Pre-
Analysis Shape servative
Chemical Plastic Large Plastic Saturated
mouthed Lids Saline
Jars
Histo- Glass According Glass Lids 10%
pathology to size of Formal
organ saline
Serology Sterilized Test Tube Glass or Anti-
glass test Rubber coagulant
tube stopper

38. 6. Labelling
Each container should be labelled indicating,
• Number of jar, 1, 2, 3, ….. Should be mentioned
• Name of specimen, site of collection
• Preservative used
• PMR / MLC no.
• Date & Time
• Name of Person
• Examination required
• Name of Doctor, Signature & Official Seal should
be affixed.

39. 7. Sealing of Specimens
• All the specimens should be sealed with Sealing
wax to avoid tempering and to maintain secret
chain of custody
• All the containers or jars should be packed in
one box, and the box should be labelled
indicating,
• Address to be sent
• Arrow showing Upside
• Box should be sealed
• Box should accompany a forwarding letter

40. Information To Be Sent Along
• The following information is to be sent in the
forwarding letter along-with the Specimens,
• a) Copy of MLR / PMR
• b) Examination required
• c) Request letter containing the bio-data, name
of specimen, etc;
• d) Copy of FIR
• e) Copy of Inquest Report
• f) Specimen of the Seal

41. 8. Despatch of The Specimens
• Specimens should be collected,
preserved, and despatched immediately
after autopsy.
• The only condition in which the specimens
are allowed to be kept is that when the
autopsy is conducted at odd hours, when
the lab is closed.

42. 9. Safe Storage
• The specimens should be kept in lock and
key in the freezers.
• The specimen should be registered
• The seal should be intact, it should be
compared with the specimen of the seal
provided.

43. 10. Transportation
• The specimens should be transported,
1.Through Police
2.Through Railway Parcel
3.Through Postal Parcel
4.Through Special Messenger by hand.

44. CHAIN OF CUSTODY
• “ Any and all who handle the specimens at
a particular instant should be able to
certify the extent of handling i.e.
• What was collected
• Why it was collected
• To whom it was handed over
• When it was handed over
• For how long it remained in custody

45. • Chain of custody should be maintained to avoid
adulteration and tempering,
• Chain of custody should be maintained till the
specimens are presented in the court
• Handling should be certified i.e. It must be on written
receipt
• Principals of chain of Custody
• Shorter the chain, Better it is
By involving less and less persons.
• Surer the chain, Better it is.
• Every surrender should be on a written receipt.

46. THANK YOU

49. SPECIAL INSTRUCTIONS

50. Examination Of Blood
Types of Cases
Criminal Cases
Physical Assaults, Sexual Assaults, Poisoning
(Homicidal, Suicidal, Accidental)
Civil Cases
Identity of the person
Inheritance
Disputed Paternity
Disputed Maternity

51. Source of Blood
1.External
On clothes
On the body
At the scene of crime
(As stains or clotted blood)
2. Internal
Peripheral veins
Direct from heart at autopsy

52. Special Instructions for Blood
collection
1. In cases of dry stains on any hard surface,
it is scrapped off with the scalpel and collected
on a glazed paper.
2. In cases where stain is wet, then it can be
collected as,
a) Let the stain be dried then scrap it.
b) A wet cotton bud in normal saline is
rolled on the stain, dry this bud in air and then
put it in a clean glass test tube, with the care it
should not touch the walls.

53. 3. When the blood is on plaster or wood, then
cut that portion of wood and chip off the plaster.
4. When the blood is on the soil or ground,
then sufficient amount of soil is collected.
5. When the stain is on clothes, then they are
allowed to dry in air, not in heat or sunlight, then
pack them in plastic bags separately.

54. 6. Disputed Paternity or Maternity
If the specimen is to be collected for disputed paternity
or maternity, then is collected from peripheral vein with
syringe.
No preservative is added except anti-coagulant e.g.;
Ca. Oxalate, Heparin
The samples of blood are collected in front of all the
constesting parties.
The sample of father is signed by mother.
The sample of mother is signed by father.
The sample of child should by both father and mother

55. 7. Poisoning
At autopsy the blood is collected direct from heart or
big veins bringing blood to the heart.
8. CO Poisoning
After collecting blood a layer of liquid paraffin is
placed over the blood to avoid evaporation.
8. Alcohol Intoxication
At the site of collection of blood from peripheral vein,
the area should not be cleaned with spirit to avoid
contamination.
9. Quantity of Blood
In living persons 10-15 ml and in case of autopsy 50-
100 ml of blood is collected.

56. EXAMINATION OF SEMEN

57. EXAMINATION OF SEMEN
• It is the most extensively studied material.
Semen coagulates immediately after
ejaculation and then liquefy in next 15
minutes.
• Both these processes are dependant
upon different enzymes in semen.
• The medico-legal importance of study of
semen is in cases of SEXUAL ASSAULTS

58. Sources of Collection
1. External
. On the Body
. On the Clothing
. At the Scene of Crime
2. Internal
. Pre-Hymenal areas
. Post-Hymenal Areas

59. Collection
• 1. The portion of fabric having the stain is cut,
dried in shade to prevent putrifection and
preserved.
• 2. If pubic hair are matted together, a portion of
hair is cut and preserved.
• 3. Dried or drying seminal stains on the body
like, medial aspects of thighs; are collected on
soaked cotton swab in saline and then dried.
• 4. Dry stains on smooth surface is scrapped
with a blunt scalpel into a glass container.

60. Swab collection
From the Genital Area, total 5 swabs are
collected,
a) Pre-Hymenal Area,
3 swabs are taken
b) Post-Hymenal Area,
2 swabs are taken

61. Collection of Swabs
• Swabs must be taken before the digital
examination and before the urine sample.
• Check for the AUTHORITY
• Take the CONSENT
• UNDRESS the patient
• Place the patient in LITHOTOMY position
• First take Pre-Hymenal Swabs
Which are 3 in number

62. • One is taken from medial sides of thighs.
• Second from the area around vulva.
• Third from pre hymenal area in the
introitus.

64. Vaginal Swabs
• PRECAUTIONS
• If the hymen is intact, do not attempt
digital examination,
• Do not attempt the use of vaginal
speculum,
• So if hymen is intact no swabs are taken.

65. • When the patient in lithotomy position,
gently separate labia,
• Introduce vaginal speculum,
• After that cotton swabs are passed
through the opening in the speculum, and
collect two swabs from high up.

66. Preparation of Slide
• From one vaginal swab which we have
collected, slides are prepared,
• Swab is rubbed in the middle 1/3 of the slide,
• Two slides are prepared,
• Slides are dried in air,
• Then they are placed facing each other with
placing match sticks in between them, so that
they should not rub with each other.

67. MATCH STICKS
SLIDE 1
. .
SLIDE 2

68. Pipette Specimen
• The specimen of semen can also be collected
from vagina with the help of pippette,
• About 20 ml of normal saline is injected into
vagina,
• After some time the specimen is collected with
the help of special pippette, which have a bulb in
between to avoid suction into mouth,
• Then this specimen is transferred to test tube,
for further processing.

69. BULB IN THE CENTER

70. CORK
SWAB
NOT TOUCHING THE WALLS
OF TEST TUBE

71. Examination of Saliva

72. • The medico- legal importance of saliva
and its trace is in both,
SEXUAL ASSAULTS
PHYSICAL ASSAULTS

73. SECRETORS’
Secretors' are those persons who secrete their
blood group substances in their body
secretions, especially
SALIVA
SEMEN
VAGINAL SECRETIONS and
TEARS
About 80% people are secretors’, and those
who does not secrete are called non-
secretors’.

74. Source of Salivary Stains
It may be found,
a) On Used Articles
• CUP OF TEA
• POSTAL ENVELOP, etc;
b) On The Eaten Food
• HALF EATEN FOOD LEFT
• EATEN APPLE
c) On The Body of Victim
• AT THE AREAS OF BITE

75. On the body of victim, Bites may be,
1) True bites
2) Love Bites
TRUE BITES
Bites between the teeth, its impression help in
identity of the person.
LOVE BITES
It’s a pressure suction between tongue and
teeth, there appear tiny areas of haemorrhages.
They are usually found over neck, breasts, chest
wall, medial sides of thighs. Salivary stains here
will help in identity.

76. Collection of stains
• Soak the cotton swab in normal saline
and role it over the stained area, dry it in
air and put in test tube.

77. Collection of Control
• The most important thing is to collect
control specimen of saliva from the
suspect.

78. Procedure of Collection Of
Control Specimen Of Saliva
• First ask the patient to wash the mouth with
normal saline, then with plain water,
• Now ask the individual to chew some inert
material, piece of paraffin, non- sugar coated
chewing gum,
• Then ask the person to loosen his facial and
oral musculature,
• Tickle the inner walls of mouth with glass rod,
• Tilt the mouth on one side, the saliva will start
flowing to the angle of mouth,
• Collect it in a glass test tube.

79. Amount to be Collected
50 – 60 ml
Preservation of Saliva
a) First place the sample test tube in hot water
bath for 10 minutes, The enzymes will be
inactivated
b) Then Centrifuge the specimen at 1500
rev/min for three minutes, Cell debris will settle
down and the supernatant is preserves
c) No preservative is added.

80. Stomach Wash or Vomitus

81. • The Medico- legal importance of stomach
wash and vomitus & its stains is in cases
of poisoning.
• The stains of vomiting may be present on
the clothes & scene of crime, clothes after
drying should be packed & sent to
chemical examiner’s lab.
• Stomach wash is collected in all cases of
poisoning, First washings of the stomach
should be preserved.
• No preservative is added to it.