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12.2 Notes - Techniques Objectives Understand the concept of antigenantibody interactions and how it is applied to species identification and drug identification List and describe forensics tests used to characterize a stain as blood Immunoassay Techniques Used for typing blood Also used for detecting drugs Combine the drug with a protein and inject it back to the individual causing it to produce antibodies EMIT - Enzyme Multiplied Immunoassay Technique Used to detect drugs in urine Antibodies added to sample If present, specific drug is bound to the antibody Enzyme labeled drug is added to urine and More antibodies bind to that Measure amount of enzyme labeled drug that is bound Value of the unbound antibodies is then used to determine the concentration of the drug originally in the urine EMIT continued Screening for marijuana (THC) THC breaks down to substances more easily excreted Major metabolite is THC -9carboxylic acid EMIT is used for that specific metabolite RIA – radioimmunoassay Uses drugs with radioactive tags Neither EMIT or RIA are drug specific and must be used with a reliable confirmation test Characterization of Bloodstains Is it blood? From what species did it come? If it is human, can it be associated to a particular individual? Determination – Color Test Benzidine color test discontinued because of carcinogenic effect Currently uses phenolphthalein called the Kastle-Meyer Based on the peroxidase like activity of hemoglobin which produces a deep pink color when applied to blood Hemastix strips – turns green with blood Determination – Light Test Luminol – produces light rather than color when viewed in dark area (luminescence) Luminol extremely sensitive Can be diluted 300,000 times Will not interfere with DNA testing Determination cont. Precipitin test – used to determine if blood is animal or human Animals produce human antiserum when injected with human antigens Gel diffusion – antibodies and antigen will diffuse toward one another in an agar gel plane forming a precipitation line or by electrophoresis Determination = Human origin Further tests to determine identity Historically used ABO and polymorphic enzymes Currently uses DNA 12.2 Questions 1. What happens when serum containing B antibodies is added to red blood cells carrying the B antigen? Will the same thing happen if serum containing B antibodies is added to red blood cells containing A antigen? Explain your answer 2. What is serology and what is its most widespread application? In what other areas related to forensic science is it finding application? 3. What is the difference between monoclonal and polyclonal antibodies? 4. Briefly describe how antibodies capable of reacting with drugs are produced in animals. 5. What immunoassay technique has gained widespread popularity among toxicologists because of its speed and high sensitivity for detecting drugs in urine? What drug is this technique frequently used to screen for? 6. What three questions must the criminalist answer when examining dried blood? 7. Name the most common color test for blood and describe how it identifies bloodstains. 8. Describe how luminal is used to detect bloodstains. 9. Name two reasons why color tests are superior to microcrystalline tests for identifying blood. 10. What is the standard test used to determine whether blood is of