Blood spatter analysis is a crucial forensic tool used to reconstruct the events of violent crimes through the examination of blood stains. Different types of blood spatter, categorized by their velocities and formation methods, provide insights into the dynamics of the crime scene such as the direction of blood, weapon type, and victim positioning. The analysis helps differentiate between various bloodstain patterns like passive, transfer, and projected stains, along with calculating angles and areas of origin to determine the sequence of events.

1. Blood spatter analysis
anusha singh

2. Introduction
Blood is one of the most important and
frequently encountered evidence. It can be
found in almost every type of crime like
murders, assaults, rape, etc. During
commission of violent crimes blood stains are
deposited on floors, walls, and other objects
on the crime scene. Analysis of blood stains
can be very useful in reconstructing actions,
that took place at the scene.
anusha singh

3. Blood stain pattern analysis
• Blood stain pattern: Blood stain pattern is a
physical geometric image created by blood
contacting the surface or surface contacting
the blood.
• Blood stain pattern analysis: It is the
interpretation of information created by blood
stain patterns.
anusha singh

4. Info obtained from bloodstain
pattern analysis
• Direction from which blood originated.
• Angle of impact.
• Nature of the force involved.
• Probable distance from the target from which
droplets originated.
• Relative position of the suspect, victim and other
related objects.
• Approximate number of blows during an incident.
anusha singh

5. • Confirm or refute the assumptions concerning
events and their sequence-
1 ) position of victims
2) evidence of struggle
• Movement of a bleeding individual at a crime
scene.
• Which wounds were inflicted first.
• Type and velocity of weapon.
• Handedness of assailant(right or left handed)
anusha singh

6. Analyzing spatter stains
Velocity of blood drops :
• The sizes of bloodstains are affected by the
external force.
• Increasing energy of external force will reduce
surface tension thus decreasing the size of
droplets.
• Bloodstains can be divided into 3 categories
based on different travelling speed:-
I. Low velocity impact spatter
II. Medium velocity impact spatter
III. High velocity impact spatteranusha singh

7. 1. Low velocity impact spatter:
• Velocity=5 feet per second
• Blood dropping from a cut finger, bleeding,
nose, other wounds.
• Stains with diameter more than 4mm.
anusha singh

8. 2. Medium velocity impact spatter:
• Velocity =25 feet per second
• Swinging knife, bat, kicking foot, swinging
hand, expirated etc.
• Stains with diameter 1mm to 4mm.
anusha singh

9. 3. High velocity impact spatter:
• Velocity =100 feet per second
• Fire arms, airplane propeller, power
equipment etc.
• Often has a misting effect appearance.
• Spatter with less than 1mm in diameter.
anusha singh

10. Determining directionality of stains:
• Directionality indicates the direction blood
was moving at the point of deposition.
• This analysis is applicable when the blood
source is projected at 0ᵒand 90ᵒ.
• In this condition resulting stain is elongated
ellipse, called parent stain.
• Additionally satellite stains in the vicinity of
the parent stain can be observed.
• When such a pattern is observed the pointed
end of spine always point towards the
direction of travel of bloodstains.
anusha singh

11. Directionality of blood drop
anusha singh

12. Determining angles of impact :
• The shapes of the spatter stains are affected
by the angle of impact.
• When a blood drop strikes surface at 90ᵒ a
circular parent stain is observed.
• As the impact angle decreases shape of stain
becomes more elongated.
• Ratio of width and length of parent stain is
proportional to sine of angle of impact.
• Sinα= w÷l ; here α is angle of impact
anusha singh

13. Angle of impact
anusha singh

14. Determining area of origin :
• Area of origin is a 3D location from which spatter
originated.
• Using simple trigonometry, area of origin can be
determined. This can be accomplished by using
by using string or tangent method.
• In string method angle of impact of each stain is
calculated.
• A string is connected between stain and surface.
Path of string indicating trajectory of stain is set
using a protactor based on calculated angle of
impact.
• For a spatter pattern generated from single event,
the strings converge. The area where strings meet
is area of origin. anusha singh

15. Area of origin of blood stains
anusha singh

16. Types of stain
• Passive bloodstains- formed due to bleeding
from wound deposited on surface under
influence of gravity
• Transfer bloodstains- resulting from contact
between a blood bearing surface and other
• Projected bloodstain- formed when a volume
of blood is deposited on a surface under a
pressure or a force that is greater than the force
of gravity
anusha singh

17. 1.Passive spatter:- Drip
Drop
Splash
Flow
Pool
2.Transfer spatter:- Swipe
Wipe
3.Projected spatter:- Impact
Cast-off
Forward spatter
Backward spatter
Expiration
Void
anusha singh

18. Drip pattern
A bloodstain
pattern resulting
from a liquid
that dripped into
another liquid,
at least one of
which was
blood.
anusha singh

19. Drop pattern
A bloodstain
resulting from
a falling drop
that formed
due to gravity.
anusha singh

20. Splash pattern
A bloodstain
pattern
resulting from
a volume of
liquid blood
that falls or
spills onto a
surface.
anusha singh

21. Flow pattern
A bloodstain
pattern resulting
from the
movement of a
volume of blood
on a surface due
to gravity or
movement of
the target.
anusha singh

22. Pool pattern
A bloodstain
resulting from
an
accumulation
of liquid blood
on a surface.
anusha singh

23. Swipe pattern
A bloodstain
pattern resulting
from the transfer
of blood from a
blood-bearing
surface onto
another surface,
with characteristics
that indicate
relative motion
between the two
surfaces. anusha singh

24. Wipe pattern
An altered
bloodstain
pattern
resulting from
an object
moving
through a pre
existing wet
bloodstain.
anusha singh

25. Impact
pattern
A bloodstain
pattern
resulting from
an object
striking liquid
blood.
anusha singh

26. Expiration
pattern
A bloodstain
pattern
resulting from
blood forced
by airflow out
of the nose,
mouth, or a
wound.
anusha singh

27. Cast-off
pattern
A bloodstain
pattern
resulting from
blood drops
released from
an object due
to its motion.
anusha singh

28. Forward
pattern
A bloodstain
pattern
resulting from
blood drops
that travelled
in the same
direction as
the impact
force.
anusha singh

29. Backward
spatter pattern
A bloodstain
pattern resulting
from blood drops
that travelled in
the opposite
direction of the
external force
applied; associated
with an entrance
wound created by
a projectile.
anusha singh

30. Void pattern
An absence of
blood in an
otherwise
continuous
bloodstain or
bloodstain
pattern.
anusha singh