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Blood Found at Crime Scene

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Presentation on theme: "Blood Found at Crime Scene"— Presentation transcript:

1 Blood Found at Crime Scene
Questions to ask: Is it really blood? Is the blood human? Who does the blood belong to? How did the blood get there?

2 Bloodstain Pattern Analysis
What is the purpose? Reconstruct crime scene Position of victim Evidence of struggle Confirm (or refute) testimony Consistency with suspect statement How is BPA possible? Blood is a liquid subject to laws of physics!

3 Types of Blood Patterns
Passive blood pattern created by gravity alone Transfer transfer blood from one surface to another by direct contact Projected blood subjected to source other than gravity

4 Passive Bloodstains Bloodstain is created with only the force of gravity drops drip patterns pools

5 Passive Bloodstains The appearance of a bloodstain may depend on the texture of the surface glass, linoleum, concrete absorbent materials: carpet, clothing, textiles

6 Transfer Bloodstains Bloodstain is the result of direct contact between a wet, bloody surface and another surface contact bleeding swipe or smear wipe smudge

7 Transfer Bloodstains May produce a recognizable image
handprint, shoeprint

8 Projected Blood Blood subjected to action or force other than gravity
Internally produced arterial spurt/gush Externally produced cast-off stain - thrown from a blood-covered object impact splatter - resulting from impact

9 Impact Splatter Size of blood stains depends on velocity Low Medium
High

10 Directionality of Bloodstains
When a spherical droplet of blood strikes a flat surface, the shape of the stain depends on the direction of travel and the impact angle.

11 Impact angle determination

12 Impact angle determination
The shape of the stain can be used to calculate the impact angle: θ

13


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