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How is Blood Evidence used in Forensics?

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?. How blood evidence is collected.

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How is Blood Evidence used in Forensics?

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  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.net/blood.html • http://www.crimelibrary.com/criminal_mind/forensics/serology/four.html • http://nobelprize.org/educational_games/medicine/landsteiner/readmore.html • http://www.faculty.ncwc.edu/TOCONNOR/425/425lect13.htm

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