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Blood Found at Crime Scene

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?. http://www.bloodsplatter.com/BPAtutorial.htm. Bloodstain Pattern Analysis. What is the purpose? Reconstruct crime scene Position of victim

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Blood Found at Crime Scene

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  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? http://www.bloodsplatter.com/BPAtutorial.htm

  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! http://www.bloodsplatter.com/BPAtutorial.htm

  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 http://www.bloodsplatter.com/BPAtutorial.htm

  4. Passive Bloodstains • Bloodstain is created with only the force of gravity • drops • drip patterns • pools http://www.bloodsplatter.com/BPAtutorial.htm

  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 http://www.bloodsplatter.com/BPAtutorial.htm

  7. Transfer Bloodstains • May produce a recognizable image • handprint, shoeprint http://www.bloodsplatter.com/BPAtutorial.htm

  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 http://www.bloodsplatter.com/BPAtutorial.htm

  9. Impact Splatter Low • Size of blood stains depends on velocity 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. http://www.bloodsplatter.com/BPAtutorial.htm

  11. Impact angle determination

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

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