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12.2 Notes - Techniques

12.2 Notes - Techniques. Objectives. Understand the concept of antigen-antibody 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

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12.2 Notes - Techniques

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  1. 12.2 Notes - Techniques

  2. Objectives • Understand the concept of antigen-antibody interactions and how it is applied to species identification and drug identification • List and describe forensics tests used to characterize a stain as blood

  3. 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

  4. 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

  5. EMIT continued • Screening for marijuana (THC) • THC breaks down to substances more easily excreted • Major metabolite is THC -9-carboxylic acid • EMIT is used for that specific metabolite

  6. RIA – radioimmunoassay • Uses drugs with radioactive tags • Neither EMIT or RIA are drug specific and must be used with a reliable confirmation test

  7. Characterization of Bloodstains • Is it blood? • From what species did it come? • If it is human, can it be associated to a particular individual?

  8. 12.1 & 12.2 Questions • 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 • What is serology and what is its most widespread application? In what other areas related to forensic science is it finding application? • What is the difference between monoclonal and polyclonal antibodies? • Briefly describe how antibodies capable of reacting with drugs are produced in animals. • 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? • What three questions must the criminalist answer when examining dried blood?

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