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, 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 little as 10 to 30 cells.
• Touch DNA samples are processed exactly 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.