Forensic Science HQ

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Forensic DNA Analysis

DNA analysis was first introduced to the U.S. courts in the early 1990’s. It is without a doubt the biggest advancement in Forensic Science since the discovery of fingerprints.

Forensic DNA STR analysis

Why is DNA analysis so important in criminal investigations?

  • A DNA profile can positively include or exclude a person as source of evidence.
  • DNA results can be obtained from a very small, old or degraded sample, and is found in almost all biological material.
  • With the exception of identical twins, no two people have the same DNA. It is unique.

What are the disadvantages of DNA analysis?

  • Cost. DNA equipment and trained personnel are not cheap, although advances in science and technology are making it more affordable every day.
  • Sensitivity. Because DNA is so prevalent and the techniques so sensitive, extreme care must be taken not to contaminate the evidence.
  • Complexity. While the interpretation of a single source of DNA is usually fairly straight forward, it can be very difficult to correctly interpret samples with multiple sources and concentrations. Forensic scientist must undergo a long, continual training program to stay current with the technology.
  • Time. Because of the complexity, DNA analysis usually takes several days at best. Also due to the demand, there is often a backlog of cases to be analyzed and a limited number of resources.

 

Forensic DNA Yield Gel

DNA Yield Gel

What types of tissue can be analyzed for DNA? There are many, but the most common are:

  • Blood
  • Saliva
  • Hair (with a root)
  • Bone
  • Teeth
  • Semen
  • Vaginal secretions

What types of evidence have been used for DNA analysis?

  • Bloodstains
  • Toothbrush
  • Beverage containers
  • Hats
  • Cheek swabs
  • Sexual assault stains
  • Gloves
  • Chewing gum
  • Cigarettes

Almost anything that comes in contact with the human body will contain traces of DNA and is a potential source of evidence.