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Blood and other bodily fluid

Blood and other bodily fluid . Forensic Characterization of Bloodstains cont’d. Micro Crystal Tests Takayama Tiechman Advantages More specific then chemical test Disadvantages Not as sensitive More susceptible to interference.

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Blood and other bodily fluid

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  1. Blood and other bodily fluid

  2. Forensic Characterization of Bloodstains cont’d • Micro Crystal Tests • Takayama • Tiechman • Advantages • More specific then chemical test • Disadvantages • Not as sensitive • More susceptible to interference

  3. Forensic Characterization of Bloodstains: Species Origin A stain is used to visualize precipitin band

  4. Forensic Characterization of Semen: 1. VISUALIZATION MANY BODY FLUIDS FLUORESCE WITH ALTERNATE LIGHTING SOURCES

  5. Forensic Characterization of Semen: 2. PRESUMPTIVE TESTING ACID PHOSPHATASE ENZYME / FOUND IN LARGE CONCENTRATIONS IN SEMEN

  6. Forensic Characterization of Semen: 3. CONFIRMATION A. MICROSCOPIC IDENTIFICATION OF SPERM B. DETECTION OF P30, A MALE PROSTATE PROTEIN. USEFULL FOR VASECTOMIZED MALES

  7. Forensic Characterization of Saliva Detection of Amylase (breaks down starch in gel) • Evidence commonly tested for the presence of saliva includes: • Cigarette butts • Envelope flaps • Swabs taken from the body of sexual assault victims • Bottles, cans, & straws Gel contains starch that is broken down (circles ) in the presence of Amylase enzyme

  8. Goals of biological evidence collection • Collect as much sample as possible from a single source—keep it concentrated • Ensure that the sample is not inadvertently mixed with other biological samples—change gloves if contaminated • Handle the sample in a manner that minimizes deterioration—air-dry quickly (and no heat or sunlight exposure)

  9. Further recommendations for collection of biological evidence • Handle as little as possible—submit the item with the stain still on it • If stain is on a large porous surface (e.g., a rug) cut out the stain area (plus unstained) • Collect with slightly moistened (with dist. water) cotton swab—keep it concentrated, and take a control swab too

  10. Taking care to avoid contamination • Don’t allow one evidence stain to come into contact with other biological samples, including transfer from tools and gloves • Don’t talk or cough over evidence stains • Collect and package stains separately • Clean tools (e.g., tweezers) thoroughly, with distilled water stream, dry with tissue, repeat • May use disposable tools

  11. Packaging biological evidence • Allow stains to air-dry as much as possible before placing in paper bag or envelope—do not use plastic • Use separate paper containers for each item and package stains and controls separately • Ensure that the paper container is large enough to allow circulation around the evidence item • For garments, use clean paper to prevent different stains from contacting each other

  12. Forensic Characterization of Semen • Many crimes involve sexual misconduct • Normal males, upon ejaculation, release seminal fluid. This fluid is a mixture of components: • water • spermatozoa • enzymes • inorganic salts • Semen at a crime scene (clothing, bed sheets, carpet, cushions) can be located and identified by three common methods: • microscope examination to find sperm • acid phosphatase test • p30 (also called prostrate specific antigen) immunoassay test

  13. Forensic Characterization of Saliva Saliva is a mixture of many components: 99% water Mucin (protein helps in swallowing) Amylase (enzyme to help digest carbohydrates) Cheek cells (good for DNA) Adults produce 1.0-1.5 liters of saliva/day and it is not uncommon at crime scenes (especially involving bite marks). A simple test for saliva involves mixing starch, iodine, and a sample of the presumed saliva together. Starch and iodine are a deep blue color when mixed together. The amylase breaks down starch, however, and the color fades (takes about 15 mins @ 37 oC).

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