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JS 112: Detection, Collection, Presumptive testing and Preservation of Biological Evidence

JS 112: Detection, Collection, Presumptive testing and Preservation of Biological Evidence. Pre-class activities Group Quiz Announcements and Assignments Learning Objectives List the sources of Biological Evidence Discuss presumptive tests utilized on biological evidence

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JS 112: Detection, Collection, Presumptive testing and Preservation of Biological Evidence

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  1. JS 112: Detection, Collection, Presumptive testing andPreservation of Biological Evidence • Pre-class activities • Group Quiz • Announcements and Assignments • Learning Objectives • List the sources of Biological Evidence • Discuss presumptive tests utilized on biological evidence • Discuss proper collection of biological evidence • Understanding how to avoid contamination • Understanding how to detect and monitor for contamination

  2. Announcements & Assignments Announcements Weds 28th Dr. John Tonkyn Assignments Read Chapters 10 and 11 View the following trainings What Every First Responding Officer Should Know About DNA Evidence AND What Every Investigator and Evidence Technician Should Know About DNA Evidence Find the training at - http://dna.gov/training/letraining/ References Saferstein R. 2004. Chapter 10 and 11 Gary Sims- Personal communication 2003.- Powerpoint slides on contamination http://www.cci.ca.gov/Reference/peb/peb.html Jeremiah Garrido 2003- Slides on presumptive testing- Santa Clara County Crime Laboratory

  3. Sources of Biological EvidenceExtra CreditEveryone that signed their team lists will get +1Members of the two top teams get +2 Bonus points still being recalculated

  4. Material Reference Blood and blood stains Budowle 1995 Semen and semen stains Budowle 1995 Bones Gill 1994 Teeth Alvarez 1996 Hair with root Higuchi 1988 Hair shaft Wilson 1995 Saliva (with nucleated cells) Sweet 1997 Urine Benecke 1996 Feces Hopwood 1996 Debris from fingernails Wiegand 1993 Muscle tissue Hochmeister 1998a Cigarette butts Hochmeister 1991 Postage stamps Hopkins 1994 Envelope sealing flaps Word 1997 Dandruff Herber 1998 Fingerprints Van Oorschot 1997 Personal Items: Razor blade, chewing gum, wrist watch, ear wax, toothbrush Tahir 1996 Sources of Biological Evidence

  5. Steps in Forensic DNA typing • (Figure 6.1 Rudin and Inman 2001) Evaluation- Is it there? 1. Start with biological sample 2. Screen- blood? Semen? Saliva, human? Extraction- Get and clean DNA 3. Open cells  Get DNA 4. Methods to get DNA and purify DNA Quantify- Determine quality and quantity? 5. Quantify- How good and how much did you get? Type to determine and compare alleles 6. RFLP vs PCR 7. Determine alleles and compare DNA types Or alleles present in samples and references Interpretation of Results

  6. Real Forensic Biologists must first screen evidence for biological fluids before DNA testing:The “Art” of Forensic Science • What are they? • Forensic Value ? • Cells • Most commonly analyzed Semen Spermatozoa Saliva Skin Cell

  7. Blood as Physical Evidence • Occurrence of a blood stain in a certain place on an item may substantiate an account of a crime • Bloodstain Pattern Interpretation: Shape, position, size or intensity of a bloodstain may support a particular sequence of events • DNA typing analysis can be used to eliminate whole groups of people as suspects

  8. Blood spatter patterns may be used to determine the position of the sourceWhere are the 10-80o drops coming from?

  9. Pointed end of a Bloodstain points in the direction of travel

  10. The Nature of Blood • Blood- A complex mixture made of cells, enzymes, proteins and inorganic substances • Liquid portion (55%) : Water • Solid portion (45%) : • Red blood cells, white blood cells, platelets • Serum: Liquid containing antibodies that separates from blood when a clot forms

  11. Nature of Blood: Function • Red blood cells (RBC): • Transports oxygen from lungs to body tissues and in turn removes carbon dioxide by taking it to the lungs. Also contain • Antigens: • proteins found of the surface of RBCs that stimulates the body to produce antibodies against it • Grouped into systems • ABO blood typing

  12. Some stains are easily detected

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