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Notes Blood and Bloodstain Pattern Analysis

Notes Blood and Bloodstain Pattern Analysis. Plasma (mainly water) Solid materials (blood cells) Erythrocytes – red; carry oxygen Leukocytes – white; fight infection Platelets - clotting. Blood composition:. Type O is considered the “Universal Donor”

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Notes Blood and Bloodstain Pattern Analysis

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  1. Notes Blood and Bloodstain Pattern Analysis

  2. Plasma (mainly water) Solid materials (blood cells) Erythrocytes – red; carry oxygen Leukocytes – white; fight infection Platelets - clotting Blood composition:

  3. Type O is considered the “Universal Donor” • Type AB is considered the “Universal Recipient”

  4. Rh factor (D antigen) • if a person has this antigen, they are considered Rh + • if not, they are Rh –

  5. Agglutination http://www.kcom.edu/faculty/chamberlain/Website/MSTUART/lect4.htm

  6. Secretors • blood type antigens found in body fluids • ~80% of the population

  7. A Forensic Scientist needs to determine:

  8. 1. Is it blood? • Kastle-Meyer color test

  9. 1. Is it blood? • Luminol Test

  10. 2. What species did it come from? • Microscopic examination

  11. Human or Animal? • This is frog blood. • Notice the nucleus is present in the cells.

  12. Human or animal? • These are human red blood cells. • Notice they don’t have a nucleus.

  13. 2. What species did it come from? • Precipitin test

  14. 3. Significance of stain patterns in blood • Confirms or refutes theories of witnesses, suspect(s) and/or victim(s) • Helps to develop or eliminate leads • Helps to reconstruct the events which led to the creation of stain patterns present at the scene.

  15. What blood evidence can tell us: • The points of origin of the blood stain patterns • Number of blows delivered in an attack • Sequence of events • Positions of person and objects

  16. What blood evidence can tell us: • Whether something was moved • Whether someone or something was blocking the spatter • If there were struggles or if someone/something was dragged • The impact angle of the drops • Location of blood source

  17. Surface Effects • Blood droplet that fell on glass

  18. Surface Effects • Blood droplet that fell on linoleum

  19. Surface Effects • Blood droplet that fell on concrete

  20. Low Velocity spatter • Usually 4 mm in size and larger • Force up to 5 feet/second

  21. Medium Velocity Spatter • 1 to 4 mm in size • Force of 5 – 25 feet/second

  22. High Velocity Spatter • 1mm in size and smaller • Force of 100 feet/second &greater • Mistlike

  23. Transfer Patterns Hand print Shoe Print

  24. Transfer Patterns • Created when a wet, bloody surface comes in contact with a second surface and leaves a distinct pattern Hair swipe

  25. Transfer patterns From a knife

  26. Transfer Patterns Screwdriver

  27. Arterial spray

  28. Directionality

  29. Directionality

  30. Blood drop animations

  31. Point of convergence and origin determination

  32. Point of Origin and Convergence

  33. Convergence

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