1. Bloodstain Pattern Analysis… Bloodspatter 1

2. Blood – Distinct Properties
Blood forms a spherical
shape (perfect circular shape)
Surface Tension causes the blood drop to pull itself in; both horizontally and vertically.

3. Overview…at the end of this unit you will be able to
Determine Height and Angle of Blood Source
Determine Direction of Blood – Directionality
Determine types of Blood Stain Patterns – low, medium and high velocity
Determine type of weapon used

4. What does a blood spatter analyst do?
Directionality

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

6. Blood Spatter Factors affecting the size of the drop…
Consider the surface
Consider if it was a single drop or multiple drops
Consider the height the drop fell

7. Blood Drop Animation. Formation of drop. Distinct blood drop pattern
Blood Drop Animation * Formation of drop * Distinct blood drop pattern * Angle of impact
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8. Blood drops fall as small spheres
Determining Distance Blood Falls
Blood drops fall as small spheres

9. Determining Distance Blood Falls
Drops form a circle when hitting surface
Size depends on height & speed of blood drop and surface it hits

10. Determining Distance Blood Falls
Blood Spatter > Distance
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

11. Determining Distance Blood Falls
Blood Spatter > Distance
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).

12. Determining Distance Blood Falls
Blood Spatter > Distance
Determining Distance Blood Falls
After approximately 7 ft or 2 m, the diameter of the blood drop remains the same

13. Effect of Surface on shape of blood drop
Blood Spatter
Effect of Surface on shape of blood drop
Smooth surface = smooth sphere
Rough surface may cause some spatter or spines

14. 1 drop of blood dropped from 12 inches, glass, cardboard and concrete….

15. 1 drop of blood dropped from 12 inches, newspaper, paper towel, and carpet ….

17. Lab Activity… Comparing diameter of blood drops from different heights
Comparing edges and diameter of blood drops on different surfaces
Comparing blood drops at different angles

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

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

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

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

23. Determining Angle of Blood (Impact) AOI
Blood Spatter > Direction
Determining Angle of Blood (Impact) AOI
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)

24. Determining the angle of impact

25. AOI = Width of blood drop / length

26. Blood Spatter > Direction
Once Directionality and AOI are determined, a string can be guided back to the point of origin.
This will show the site of blood origin and angle the victim was positioned.

27. Using the AOI and directionality of blood drop; one can determine the height of the source (victim?)

29. Blood Spatter
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

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

31. Blood Spatter
Spattered Blood
In general, the higher the velocity the more spread out the droplets are and the individual stains are smaller.
Low impact/low velocity 7mm+ – 3.1 mm
Medium impact/medium velocity 3.0 – 1.1 mm
High impact/high velocity = gunshot <1mm

32. Low velocity… Droplets are 3.1mm in diameter or larger
beating or hitting
(after the first blow)

33. Medium velocity…. Droplets are 1.1-3 mm in diameter
Caused more by force
and less by gravity
blunt force trauma, i.e.
baseball bat, ‘billy club’,
stabbings

34. High velocity… less than 1mm in diameter takes on a "mist like"
appearance
gunshot

35. Blood Spatter
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.

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

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

38. Blood Spatter
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.

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

40. Blood Spatter
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.

41. Transfer - Wipe or a swipe..
Transfers occur when
a blood source comes in
direct contact with a target
surface area.
Blood is moved or ‘transferred’
to a new surface

42. Alteration of bloodstain over time
Blood Spatter
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.

43. Blood spatter tutorials:
patter.do
Dexter - Arterial Spurts
Dexter - Cast Off Stains
Expiratory Blood
Blood Swipe/Wipe
Blood Shadowing and Ghosting
Point of Impact
Blood Transfer