1. Blood Spatter

2. Blood spatter patterns
Help to reconstruct the series of events surrounding a shooting, stabbing or beating
First reference to blood spatter analysis was in 1894
Blood spatter evidence was used by the defense in the Sam Shepard case in 1955 to help exonerate him.

3. Blood Spatter patterns
Makes it possible to determine:
the direction the blood was traveling
the angle of impact
the point of origin of the blood
The manner of death, based on blood velocity

4. Blood drops Blood is a thick mixture of blood cells and plasma
When a person is bleeding, gravity acts on blood, pulling it downward, making it longer than it is wide
Blood is cohesive, so it “sticks together” and doesn’t separate as it falls
Blood maintains a round appearance when it falls on a flat surface

5. Satellites
Small secondary droplets that have overcome the force of cohesion and separated from the main droplet of blood

6. Six Patterns of Blood Spatter
Circular Drops – produced by blood falling directly to the floor at a 90 degree angle
- secondary satellites will be produced if the surface is textured
- this is known as passive fall

7. Patterns (continued)
Arterial spurts or gushes found on walls or ceilings
- caused by the pumping action of the heart

8. Patterns (continued) Splashes – shaped like exclamation points.
- the shape and position of the spatter pattern can help locate the position of the victim at the time of attack

9. Patterns (continued)
4. Smears – left by a bleeding victim depositing blood as he or she touches or brushes against a wall or furniture

10. Patterns (continued)
Trails – left by a bleeding victim as they move from one location to another
- droplets could be round or smeared or even appear as spurts

11. Patterns (continued)
6. Pools of blood – form around a victim who is bleeding heavily and remains in one place

12. More Patterns 
Fine mist – produced by high velocity impact, like a gunshot wound
Low velocity pattern – produced by a beating with a pipe
Voids – empty spaces in a spatter pattern that help determine if something was moved after the attack

13. Examination of Directionality of Blood
The shape of an individual drop of blood can provide important clues in an investigation.
As moving blood strikes a surface, several forces affect the droplet of blood:
Cohesion – force between two similar substances
Adhesion – force between two unlike surfaces
Surface tension – an elastic characteristic along the outer edge of a liquid casued by the attraction of like molecules

14. Lines of Convergence
The location from which the blood originated can be determined if there are at least two blood spatters.
Draw straight lines down the long axis of the blood spatter and note where the lines intersect – this indicates the lines of convergence

15. Crime Scene Investigation of Blood
Even after washing a room of visible blood, some blood evidence remains
Luminol – causes hemoglobin (the iron containing portion of the blood) to fluoresce under black light

16. Steps in Investigating Blood left at a Scene
Confirm the stain is blood
Confirm that the blood is human blood
Determine the blood type
Perform a DNA analysis if necessary and if DNA can be isolated from the sample