Touch DNA refers to the DNA that is left behind from skin cells when a person touches or comes into contact with an item. However, since Touch DNA (also referred to as wearer or contact DNA) is invisible to the naked eye, and is usually deposited in smaller amounts than the DNA found in bloodstains or other body fluids, it is more difficult to identify areas where skin cells may be present. As such, it can be quite challenging to obtain DNA profiles from these samples. Obtaining successful Touch DNA results depends on recognizing items which may be suitable for Touch DNA analysis, proper collection/storage of these items, and the subsequent use of the optimal sampling technique that will recover the highest number of skin cells.
Touch DNA: Forensic Collection and Application to Investigations
Williamson A. L. Touch DNA: Forensic Collection and Application to Investigations. J. Assoc. Crime Scene Recon., 2012, 18(1), 1-5.