Friday 24 August 2012

Emedinews:Insights on Medicolegal Issues:What is Touch DNA



Locard’s Exchange Principle states that with contact between two items, there will always be an exchange. So, when a crime is committed, if the perpetrator deposits a sufficient number of skin cells on an item at the scene, and that item is collected as possible evidence.
  • It is the DNA in skin cells that is left at a crime scene and may be sampled from a variety of items including gun grips, steering wheels, eating utensils, luggage handles and clothing.
  • Humans shed tens of thousands of skin cells each day, and these cells are transferred to every surface with which human skin comes into contact.
  • Touch DNA is not Low Copy Number DNA (LCN DNA).
  • LCN DNA profiling allows a very small amount of DNA to be analyzed, from as few as 10 to 30 cells.
  • Touch DNA samples are processed exactly in the same way as blood, semen, saliva etc, and can stand up to scrutiny in court much better than LCN DNA.
  • Touch DNA analysis may be able to link the perpetrator to the crime scene, by collecting the skin cells and analyzing them.

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