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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