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How is Blood Evidence used in Forensics?

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How is Blood Evidence used in Forensics? Provide information about how blood ... http://www.crimelibrary.com/criminal_mind/forensics/serology/four.html ... – PowerPoint PPT presentation

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Title: How is Blood Evidence used in Forensics?


1
How is Blood Evidence used in Forensics?
  • Provide information about how blood evidence is
    collected, categorized and compared.
  • How do scientists determine if a fluid is blood?
  • Are those tests foolproof?

2
How blood evidence is collected
  • Blood pool collect with gauze pad or clear
    cotton. Let air dry and refrigerate of freeze
    within 48 hours.
  • Dried blood wrap object in clean paper and place
    in paper bag.
  • Small object, send whole object in.
  • Large object, cover with paper and tape down or
    scrape it off with a knife.

3
How blood evidence is categorized and compared
  • Bloodtypes- A, B, AB, or O
  • Antiserum A or Antiserum B to determine type
  • Rh factor is most commonly know antigen but there
    are over 256.
  • Dried blood-
  • Heat sample to break antibody antigen bonds
  • Add know blood group to see what coagulates.

4
How scientist determine if a fluid is blood
  • Use Luminol to determine if blood is present, but
    once luminol is used it destroys the blood for
    further testing.
  • Takes 5 second to read.
  • Luminol cause blood to glow.
  • Dried blood
  • Takayama and Teichmann -crystallization test
  • Kastle-meyer chemical phenophthalein turns it
    pink if there is evidence of blood.
  • Precipitin determines if it is animal or human
    blood

5
Foolproof?
  • No
  • Other substances may react with chemical used
  • Blood degrades
  • Evidence of Chimerism
  • Secretors

6
Websites used
  • Collection and Preservation of Blood Evidence
    from Crime Scenes, by George Schiro, Forensic
    scientist Louisiana State police Crime
    Laboratory http//www.crime-scene-investigator.ne
    t/blood.html
  • http//www.crimelibrary.com/criminal_mind/forensic
    s/serology/four.html
  • http//nobelprize.org/educational_games/medicine/l
    andsteiner/readmore.html
  • http//www.faculty.ncwc.edu/TOCONNOR/425/425lect13
    .htm
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