Obtaining DNA profiles from skin cells
left behind on crime scene
items that have been touched or come into contact with the skin
is commonly referred to as “touch DNA” analysis. The ability of analysts to obtain DNA profiles from such items has opened up a world of possibilities for officers to use to link people to crime scenes. However, this powerful tool does have limitations. In this issue, we explore the obstacles associated with touch DNA as well as provide assistance for its appropriate use. A good guide to follow when investigating most crime scenes for DNA (particularly property crimes) is to look for something that a suspect left behind in the commission of the crime. There is a “best evidence” preferred order of collection. First, look for blood. Second, look for items that may have saliva contact, such as cigarettes, bottles/cans, or gum. Lastly, if blood and/or saliva contact items are not present, then you MAY consider items for “touch DNA” analysis, which is the least preferred DNA source. The reason touch DNA is the least preferred DNA source is because the person has to touch the item for an extended period of time and/or repeatedly touch the item several times to leave a sufficient amount of skin cells
to generate a usable DNA profile. Shirt collars, hats, and masks are considered acceptable for touch DNA, since those items are expected to have come into contact with the skin
for a long period of time and are expected to have been used by only one person.
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