1. Bloodstains Pattern Analysis

2. Questions Answered by Blood Spatter Interpretation
The distance between the target surface and the origin of blood
The point(s) of origin of the blood
Movement and direction of a person or an object
The number of blows, shots, etc. causing the bloodshed and/or the dispersal of blood.
Type and direction of impact that produced the bloodshed
The position of the victim and/or object during bloodshed
Movement of the victim and/or object after bloodshed

3. Summary
Establish the relationship between dropping height and blood drop diameter
Differentiate between high velocity and medium velocity impact spatter
Recognize patterns around the drop, such as satellite spatter or spines
Create and examine vertical blood drop patterns on various textured surfaces
Identify a point of convergence and point of origin

4. Blood Droplet Characteristics
A blood droplet will remain spherical in space until it collides with a surface
Once a blood droplet impacts a surface, a bloodstain is formed.
A droplet falling from the same height, hitting the same surface at the same angle, will produce a stain with the same basic shape.
How will the shape change as the height is increased or decreased?

5. Types of Bloodstain Patterns
Passive Bloodstains
Patterns created from the force of gravity
Drop, series of drops, flow patterns, blood pools, etc.
Projected Bloodstains
Patterns that occur when a force is applied to the source of the blood
Includes low, medium, or high impact spatters, cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound.
Transfer or Contact Bloodstains
These patterns are created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part.
A wipe pattern is created from an object moving through a bloodstain, while a swipe pattern is created from an object leaving a bloodstain.
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6. Conditions Affecting Shape of Blood Droplet
Size of the droplet
Angle of impact
Velocity at which the blood droplet left its origin
Height
Texture of the target surface
On clean glass or plastic—droplet will have smooth outside edges
On a rough surface—will produce scalloping on the edges

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

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

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

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

13. Blood Spatter/ Velocity
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

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

15. Blood Spatter/ Velocity
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

16. Impact spatter
Results from the application of energy to a source of wet blood
Arises from kicking, punching, or firearms
Mist – very fine spatter (.01 mm)
Usually a product of a gunshot
Fine – mainly 2mm or less
Suggestive of beating type assault
Medium – 2mm – 6mm in diameter
Suggestive of weapon cast off
Large - >6mm
Suggestive of dripping blood
Note that sneezing or coughing could cause similar patterns as above

17. Low Velocity Spatter Gravitational pull up to 5 feet/sec.
Relatively large stains 4mm in size and greater
Low Velocity Spatter
Gravitational pull up to 5 feet/sec.
Relatively large stains 4mm in size and greater

18. Medium Velocity
Force of 5 to 25 feet/sec.
Preponderant stain size 1 to 4mm in size
Beating and Stabbing Spatter = larger individual stains
First blow usually doesn’t result in spatter since there is not yet any exposed blood

19. High Velocity
Force of 100 feet/sec. and greater Preponderant stain size 1mm in size and smaller Mist like appearance
Gunshot Spatter = can result in a mist-like spatter that indicates a gunshot.

20. Blood Spatter/ Velocity
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.
Gunshots result in back spatter (where bullet enters) and forward spatter (where bullet exits).

21. 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.

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

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

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

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

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

27. Determining Direction of Blood
Blood Spatter > Direction
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)

28. Bloodstain Patterns The shape of a blood drop:
Round—if it falls straight down at a 90 degree angle.
Elliptical—blood droplets elongate as the angle decreases from 90 to 0 degrees; the angle can be determined by the following formula:

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

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

31. Blood Spatter/Other Types
Other 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.

32. Arterial Blood
Patterns are caused by the pressure within the arterial system
Will depend on:
Damage to the artery
Site of the injury
Presence of clothing
Direction of spurting
Distance of target surface
Patterns are usually the same size

33. Contact
Contact smears usually arise from contact of a bloodstained item with a non-bloodstained surface
Can leave imprint evidence

34. 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.