1. Blood Spatter Analysis
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Questions?
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3. Unknown Stain at a Scene
Questions to be answered:
1.Is it blood?
2.Is it human blood?
3.Whose is it?
Determine blood type, alcohol content, drugs present
Determine the method(s) in which blood may have been deposited
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4. Presumptive Tests for Blood Determination
Kastle-Meyer color test—a mixture of phenolphthalein and hydrogen peroxide; the hemoglobin will cause the formation of a deep pink color if blood is present
Hematest® tablet—reacts with the heme group in blood causing a blue-green color
Luminol test—reaction with blood to produce light
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5. Population Distribution of Blood Types in the U.S.
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How to Read Results
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8. Blood Droplet Characteristics
A blood droplet will remain spherical in space until it collides with a surface
COHESIVE-sticks to itself
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9. Conditions Affecting Shape of Blood Droplet
Force-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
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10. 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
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11. Bloodstain Terminology
Angle of impact—angle at which blood strikes a target surface. (900 vs 450)
Backspatter—blood that is directed back toward the source
Point of origin-place where blood leaves the body
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Blood Evidence
Class evidence for blood would include blood type. If you can determine the DNA you would have individual evidence.
Blood stain patterns are considered circumstantial evidence in a court room. Experts could argue many points including direction of travel, height of the perpetrator, position of the victim, left/right hand, whether the body was moved, etc.
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