Bloodstain pattern analysis examines the shapes and sizes of blood drops to reconstruct crime scenes. The size of blood drops depends on the distance fallen and volume of blood, though distance cannot be precisely measured. Direction of travel can be determined by the narrow end of drops. Types of patterns include spatter, castoff, and expirated blood, which provide clues about the mechanism that produced them, such as stabbings, beatings, or gunshots. Analysis of bloodstain patterns is used to determine the location of the blood source and positions of the assailant and victim.

1. Bloodstain Pattern
Analysis

2. Summary
 What is Blood?
 Determining Distance of Blood
 Determining Direction of Blood
 Types of Blood Stain Patterns

3. What is Blood?

4. Introduction to Blood

5. Blood Spatter (or splatter)
Blood drops form different shapes and sizes
Blood spatter analysis uses the shapes and
sizes to reconstruct the crime scene.

6. Determining Distance Blood Falls
Blood drops fall as small spheres
Blood Spatter > Distance

7. Determining Distance Blood Falls
 Drops form circle when hitting surface
 Size depends on speed of blood drop
Blood Spatter > Distance

8. Determining Distance Blood Falls
Faster drop = larger diameter (size)
Higher distance = larger diameter
Due to air resistance, speed maxes out at
distances above about 7 feet
Blood Spatter > Distance

9. Determining Distance Blood Falls
However, size of drop also depends on the
volume of the drop.
Volume depends on the object blood
originated from (needle = small; bat = large).
Blood Spatter > Distance

10. Determining Distance Blood Falls
Since the volume of blood is unknown…
The distance a drop has fallen
cannot be measured.
Blood Spatter > Distance

11. Effect of Surface
 Smooth surface = smooth sphere
 Rough surface may cause some splatter
Blood Spatter

12. Determining Direction of Blood
Narrow end of a blood drop will point in the
direction of travel.
Blood Spatter > Direction

13. Determining Direction of Blood
If more than one drop (from spatter) results,
the point of origin can be determined
Blood Spatter > Direction

14. Determining Direction of Blood
If more than one drop (from spatter) results,
the point of origin can be determined
Blood Spatter > Direction

15. Determining Direction of Blood
This is a 2-dimensional point of origin.
It is possible to determine the 3-D point of origin
Blood Spatter > Direction

16. Determining Direction of Blood
 The angle can be determined
mathematically.
 Width/Length, then take the
inverse sin (sin-1
).
 This number is the impact
angle (90 = perpendicular to
surface; <10 at a sharp angle)
Blood Spatter > Direction

17.  For each blood
drop, a string can
be guided back to
the point of origin.
Blood Spatter > Direction

18. Types of Spatter
 Spattered Blood = random distribution of
bloodstains that vary in size
 Amount of blood and amount of force affect
the size of blood spatter.
 Can result from gunshot, stabbing, beating
Blood Spatter

19. Spattered Blood can:
 Help determine the location of the origin of
the blood source.
 Help determine the mechanism which
created the pattern.
Blood Spatter

20. Spattered Blood
In general, for higher impacts, the pattern is
more spread out and the individual stains
are smaller.
Low impact = beating
High impact = gunshot
Blood Spatter

21. Types of Spatter
Gunshot Spatter = can result in a mist-like
spatter that indicates a gunshot.
 Not all gunshots will result in misting.
 If misting is present, it is most likely a
gunshot.
Blood Spatter

22. Gunshot Spatter
Gunshots result in back spatter
(where bullet enters) and forward
spatter (where bullet exits).
Blood Spatter

23. Types of Spatter
Beating and Stabbing Spatter = larger
individual stains
First blow usually doesn’t result in spatter
since there is not yet any exposed blood.
Blood Spatter

24. Types of Spatter
Satellite Spatter = free falling drops of blood
that fall onto a spatter pattern.
 These drips are usually much larger than
impact spatter.
 However, blood dripping into blood can
create a spatter.
Blood Spatter

25. Types of Spatter
Castoff Pattern = Blood flung off of
swinging object.
Can reconstruct where assailant and victim
were positioned.
Blood Spatter

26. Types of Spatter
Expirated Bloodstain Pattern = Blood can
accumulate in lungs, sinuses, and airway.
Forcibly exhaled.
 Can appear like beating or gunshot pattern.
 May be mixed with saliva or nasal
secretions.
Blood Spatter

27. Alteration of bloodstain over time
 Blood dries and clots over time.
 Difficult to estimate the time the blood exited
the body.
 Clotted smears can indicate time of movement.
Blood Spatter