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JS 113: Detection, Collection, Presumptive testing and Preservation of Biological Evidence

JS 113: Detection, Collection, Presumptive testing and Preservation of Biological Evidence. Pre-class activities Quiz Announcements and Assignments for next week Learning Objectives List the sources of Biological Evidence Discuss presumptive tests utilized on biological evidence

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JS 113: Detection, Collection, Presumptive testing and Preservation of Biological Evidence

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  1. JS 113: Detection, Collection, Presumptive testing andPreservation of Biological Evidence • Pre-class activities • Quiz • Announcements and Assignments for next week • 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 • Assignments and Announcements • Visit the following document on collection of biological evidence- http://www.cacnews.org/wordfiles/DNA%20SampleHandling.doc • Each team member should take a section and summarize it in 300 words. Write a total of 5 questions and answers based on your reading • 10/31 Laboratory 5A – Serology – Presumptive Testing for biological fluids • 11/05 Student Led Review for Exam 2 : • C5-Org, 6 Inor, 8 trace, 9 drugs, 10 tox, 12 serology, 15 impression, Tom Abercrombie(with 9) and Sandra Sachs (with 10)lectures- Shoeprint lab (with 15), Trace lab (with 8) • 11/07 Exam 2 References • Forensic DNA Analysis. Rudin, N. and K. Inman. 2nd Edition. 2001. ISBN: 0849302331 Publisher: CRC Press; 2nd edition (December 21, 2001) C1 and C2 • Forensic DNA Typing: Biology and Technology Behind STR Markers John Butler PhD. 2001. ISBN: 0-12-147951-X Academic Press –Figure and references on DNA sources • Saferstein R. 2004. Chapter 3 • Gary Sims- Personal communication 2003.- Powerpoint slides on contamination • http://www.cci.ca.gov/Reference/peb/peb.html • Jeremiah Garrido- Santa Clara County Crime Laboratory

  3. Biological Fluids ? • What are they? • Forensic Value ? • Cells • Most commonly analyzed Semen Spermatozoa Saliva Skin Cell

  4. 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

  5. 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

  6. Antigen & Antibody Components of Blood For every antigen there is a specific antibody

  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. Shape, Position, Size ?

  9. Neck incisions (scene)

  10. Forensic Characterization of Bloodstains Forensic Characterization of Bloodstains • IS THIS STAIN BLOOD? • WHAT SPECIES? • IF HUMAN ORGIN WHO DEPOSITED THE BLOOD?

  11. Forensic Characterization of Bloodstains Three ways of characterizing a possible bloodstain: • Chemical Color Tests or Crystal Test • Based on presence of hemoglobin • Species Determination • Based on Antigen-Antibody Reaction • Individualizing bloodstain • DNA analysis and calculating statistics

  12. Forensic Characterization of Bloodstains:Is This Blood?? • Chemical color tests • Based on hemoglobin's peroxidase-like activity (Peroxidase: enzyme that oxidizes organic compounds) • Ex: Lab/phenolphthalein, O-tol Crime Scene/Hemastix • Advantage: very sensitive • Disadvantage: • false positive rxn • Potato/Horseradish • Strong oxidizers like bleach

  13. Forensic Characterization of Bloodstains cont’d • Luminol Test • Produces light rather than color • Typically sprayed onto suspected stains to reveal stains & patterns LIGHT EMISSION

  14. STAIRCASE INTO BASEMENT Can we say it’s human blood? LIGHT EMISSION

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