Blood as Evidence Blood Pattern and Spatter Analysis for solving Crime Scenes

1. Blood Spatter Analysis
Prashant Mehta
Assistant Professor, National Law University

2. A field of forensic examination of the shapes, locations,
and distribution patterns of bloodstains, in order to
provide an interpretation of the physical events which
gave rise to their origin.

4. PROPERTIES OF BLOOD
• 8% of total body weight
• 5-6 liters of blood for males
• 4-5 liters of blood for females
• 40% blood volume loss,
internally or externally required
to produce death.
• 1.5 L loss will cause
incapacitation.
• A cut vein or artery will result in
a loss of ½ L per minute.

5. INJURIES, DEATH AND BLOOD
• Dead people do not bleed.
• If a body part is struck with an object the first blow will not cause blood spatter.
• Spatter occurs after the first blow when the wound begins to bleed.

6. SURFACE TENSION
• Blood will not break up unless it is acted upon by force. The force must be great enough to overcome the
surface tension of the blood.
• Blood forms a spherical shape (perfect circular shape) almost immediately upon separating from the
blood source. The spherical shape is caused by the surface tension of the blood.
• Surface Tension causes the blood drop to pull itself in; both horizontally and vertically.
The blood drop will settle into a spherical shape, as a result of the surface tension.
• The surface tension will maintain the sphere shape of the blood drop until it impacts with the surface.
• Blood Surface tension is 0.058 N/m.

7. VISCOSITY
• Viscosity is defined as a fluid’s resistance to flow. The more viscous a substance is,
the more slowly it will flow. The SI unit for viscosity is the Pascal second. Fluid
viscosity is compared to water that has a viscosity of one. Blood is thicker than
water and is viscous primarily due to the cellular component. Blood Viscosity is 3-4
Pascal second.

8. DENSITY
It is defined as mass per unit volume. The density of water is 1000 kg/m3. The
density of blood is proportional to the total protein concentration or cellular
component of blood and is influenced only to a minor extent by other ions, gases
etc. that are dissolved in the plasma. The average density of whole blood for a
human is about 1060 kg/m3.

9. TERMINOLOGY
• Angle of impact: angle at which blood strikes a target surface
• Bloodstain transfer: when a bloody object comes into contact with a surface and leaves a
patterned blood image on the surface
• Back-spatter: blood that is directed back toward the source of energy
• Cast-off: blood that is thrown from an object in motion
• Directionality—relates to the direction a drop of blood travels in space from its point of origin
• Contact stain: bloodstains caused by contact between a wet blood-bearing surface and a
second surface that may or may not have blood on it
 Transfer—an image is recognizable and may be identifiable with a particular object
 Swipe—wet blood is transferred to a surface that did not have blood on it
 Wipe—a non-blood-bearing object moves through a wet bloodstain, altering the
appearance of the original stain

10. WHAT DOES IT TELL US?
1. Type and velocity of use of weapon
2. Number of blows
3. Handedness of assailant (right or left-handed)
4. Position and movements of the victim and assailant during and after the attack
5. Which wounds were inflicted first
6. Type of injuries
7. How long ago the crime was committed
8. Whether death was immediate or delayed
Reconstruction could tell some more..
1. Distance from the blood source to the target
2. Direction of travel and impact angles
3. Nature of the force used to cause the bloodshed
4. The object used to cause the bloodshed
5. Sequencing of multiple bloodshed events
6.Interpretation of contact or transfer patterns

11. DROP OF BLOOD
• Parent Drop – The droplet from
which a satellite spatter
originates.
• Satellite Spatters – Small drops
of blood that break of from the
parent spatter when the blood
droplet hits a surface.
• Spines – The pointed edges of a
stain that radiate out from the
spatter; can help determine the
direction from which the blood
traveled.

12. tail points in
direction of
travel
one exception!

13. Categories of Bloodstains
• Passive
• Transfer
• Projected
• Spatters are created when blood is
acted upon by force, and travels
through the air before landing on a
target surface.
• Transfers occur when a blood source
comes in direct contact with a target
surface area.

14. PASSIVE BLOODSTAINS
• Passive bloodstains are drops created or formed by the force of gravity
acting alone.
• Projected bloodstains are created when an exposed blood source is subjected to
an action or force, greater than the force of gravity. (Internally or Externally
produced).
• The size, shape, and number of resulting stains will depend, primarily, on the
amount of force utilized to strike the blood source.
Passive Patterns:
• Drops
• Drip patterns
• Pools
• Clots

15. Drops Drip
Clots Pool
Types of Passive Blood Stains

16. TRANSFER BLOODSTAINS
• A transfer bloodstain is created when a wet, bloody surface comes in
contact with a secondary surface.
TYPES OF TRANSFER BLOOD STAINS
• Contact bleeding
• Swipe or smear
• Wipe / Smudge
• Back Spatter

17. Contact Bleeding Swipe / Smear
Wipe / Smudge Pool
Types of Transfer Blood Stains

18. Other Patterns
Back Spatter Transfer

19. PROJECTED BLOOD
• Projected bloodstains are created when an exposed blood source is
subjected to an action or force, greater than the force of gravity. (Internally
or externally produced.)
• The size, shape, and number of resulting stains will depend, primarily, on
the amount of force utilized to strike the blood source.

20. Droplets could be altered..
1. Size of the droplet
2. Angle of impact
3. Velocity at which the blood droplet left its origin
4. Height
5. Texture of the target surface
1. On clean glass or plastic—droplet will have smooth outside
edges
2. On a rough surface—will produce scalloping on the edges

21. LARGE VOLUMES OF BLOOD
Patterns created by same volume of blood from the same source to target distance
Dripped Blood Spilled Blood

22. TARGET SURFACE TEXTURE
• Bloodstains can occur on a variety of surfaces, such as carpet, wood, tile,
wallpaper, clothing, etc.
• The type of surface the blood strikes affects the amount of resulting spatter
including the size and appearance of the blood drops.

23. TARGET SURFACE TEXTURE
• Blood droplets that strike a hard smooth surface, like a piece of glass, will
have little or no distortion around the edge.

24. TARGET SURFACE TEXTURE
• Blood droplets that strike linoleum flooring take on a slightly different
appearance. Notice the distortion (scalloping) around the edge of the blood
droplets.

25. TARGET SURFACE TEXTURE
• Surfaces such as wood or concrete are distorted to a larger extent. Notice
the spines and secondary spatter present.

26. ARTERIAL SPURT/GUSH
• Bloodstain patterns resulting from blood exiting the body under
pressure from a breached artery.

27. CAST-OFF STAINS
• Blood released or thrown from a blood-bearing object in motion.

28. IMPACT SPATTER
Blood stain patterns created when a blood source receives a blow or force
resulting in the random dispersion of smaller drops of blood.It depends on
spreading behaviour / surface texture and velocity

29. Stages of Drop Impact
Contact & Collapse Displacement
Image used with permission from Tom Bevel & Ross Gardner, June 2006.

30. Stages of Drop Impact
Dispersion Retraction
Image used with permission
from Tom Bevel & Ross
Gardner, June 2006.

31. LOW VELOCITY IMPACT SPATTER
Low velocity spatter is about 5 ft / second and usually 3 mm or greater in
diameter and indicates blood is dripping. Low impact is really blood under the
influence of gravity - it just falls.

32. MEDIUM VELOCITY IMPACT SPATTER
Medium velocity spatter is 5 – 25 ft / second with a <3 mm diameter and
usually indicates blunt trauma or sharp trauma or it could be cast-off. Medium
impact occurs when a force such as a bat is applied.

33. HIGH VELOCITY IMPACT SPATTER
Force of 100 feet/sec and greater. Preponderant stain size 1 mm in size and
smaller. Mist like appearance.

34. DIRECTIONALITY OF BLOODSTAINS
• When a droplet of blood strikes a surface perpendicular (90 degrees) the
resulting bloodstain will be circular.
• That being the length and width of the stain will be equal.

35. DIRECTIONALITY OF BLOODSTAINS
• Blood that strikes a surface at an angle less than 90 degrees will be
elongated or have a tear drop shape.
• Directionality is usually obvious as the pointed end of the bloodstain (tail)
will always point in the direction of travel.

36. IMPACT ANGLE DETERMINATION
• The angle of impact is the acute angle formed between the direction of the
blood drop and the plane of the surface. The more acute the angle, the
easier it is to determine the direction of travel.
• By utilizing trigonometric functions its possible to determine the impact
angle for any given blood droplet.
• SIN < = opp (a)/hyp (c)

37. Angle of Impact

38. Directionality: Impact Angle Determination
sin θ = W / L
What does W = L mean?
sin θ = 1 → θ = 90°
Drop is a circle!

39. IMPACT ANGLE DETERMINATION

40. POINT OF CONVERGENCE
AND ORIGIN DETERMINATION
• The common point, on a 2 dimensional surface, over which the directionality
of several bloodstains can be retraced.
• Once the directionality of a group of stains has been determined, it’s
possible to determine a two dimensional point or area for the group of
stains.

43. POINT OF CONVERGENCE AND
ORIGIN DETERMINATION

45. Origin Determination
• The common point, on a 2 dimensional surface, over which the directionality of
several bloodstains can be retraced.
• Once the directionality of a group of stains has been determined,
it's possible to determine a two dimensional point or area for the group of stains.
• By drawing a line through the long axis of a group of bloodstains the point of
convergence can be determined. Where the lines of the group of stains intersect one
another the convergence point can be established.

47. Is it Blood – Kastle Meyer Test
The Kastle-Meyer test is a presumptive blood test, first described in
1903, in which the chemical indicator phenolphthalein is used to detect the
possible presence of hemoglobin.
It relies on the peroxidase-like activity of hemoglobin in blood to catalyze the
oxidation of phenolphthalin (the colorless reduced form of phenolphthalein)
into phenolphthalein, which is visible as a bright pink color.

48. Whose Blood it is? Human / Animal
• To determine if the blood is human, it is necessary to produce anti-human
antibodies. Injecting some human blood into a different animal, a rabbit for
example does this. When human blood is injected into the rabbit, the rabbit
produces anti-human antibodies or anti-serum.
• To perform the precipitin test, a sample of the suspected human blood in placed
in the depression of a gelatin coated depression slide. Anti-human antibodies or
anti-serum if placed on the opposite side of the depression slide. After applying an
electric current, the protein molecules in the two samples migrate towards each
other forming a precipitin line where the proteins combine (antigen and
antibodies).

49. Is there Hidden Blood
• When using luminol to test for blood the area of suspicion must be darkened. The
luminol mixture is sprayed onto the suspect area and when the bloodstain comes
into contact with the luminol there is an emission of bright blue light.
• When luminol is being used to detect blood, the catalyst for the reaction is
haemoglobin. Haemoglobin is a molecule that contains iron and is found in red
blood cells.
• The chemical reaction is an example of chemiluminescence.
• Chemical Structure: Luminol’s (C8H7N3O2) scientific name is 5-amino-2,3-dihydro-
1,4-phthalazine-dione.