Year 9 Forensic Psychology Case 1

Topic 1: Forensic Biology

DNA - deoxyribonucleic acid

  • DNA is located in the nucleus
  • DNA is used in crimes to rule out or connect suspects

DNA Profiles

  • A DNA profile is a summary of one person’s genetic information
  • CODIS stands for Combined DNA Index System, which stores information about a variety of peoples DNA and genetic makeup
  • Markers are used within DNA profiles - 13 in each

Processing DNA

  • There are four steps to processing DNA - extract, amplify, separate, analyze
  • An example of how DNA is collected is from the cheek with a buccal swab
  • A technique called Polymerase Chain Reaction is used to copy DNA markers
  • A genetic analyzer is used to sort DNA markers by size

Toxicology

  • Forensic toxicologists test human tissues and fluids for the presence of drugs and chemical substances
  • Many substances can be tested, but the most common ones are vitreous humor, blood, and urine
  • DIfferent amounts of each substance are drawn:
    • 2 mL of vitreous humor
    • 30 mL of blood
    • 30 mL of urine
  • Some other things that may be tested are maggots and stomach contents
  • Headspace Gas Chromatography is used to test for the presence of alcohol
  • An Elisa test can determine if certain categories of drugs or chemicals are present in a sample, e.g. opioids
  • the GC/MS instrument confirms specific drugs and their presence

Every single chemical has its own specific pattern of mass spectrum, determined with the GC/MS instrument

Firearms and Tool Marks

  • rifling on guns can be found at the edge of the barrels
  • cartridges are found in the magazines
  • the primer produces the spark to ignite the gunpowder, and the bullet diameter is used to determine the caliber
  • striations are tiny microscopic scratches on the surfaces of bullets
  • rifling impressions are impressions left on the bullet after its been fired

Medical Examiner

  • the first thing a medical examiner does is conduct an external examination
  • 40% of deaths are accidental
  • 9% of deaths are homicides