Touch DNA: Forensic Collection and Application to Investigations

Introduction Various Touch DNA sampling techniques have been used at the crime scene and in forensic laboratories worldwide for over a decade [1]. The recent success of using Touch DNA collection methods to obtain DNA profiles from high profile cases including the exoneration of Timothy Masters and the JonBenet Ramsey homicide investigation has created an increased interest in better understanding the science of Touch DNA and its potential evidentiary value. Humans shed tens of thousands of skin cells each day and these cells may be transferred to surfaces our skin contacts. When a crime is committed, the perpetrator may deposit a sufficient number of skin cells on an item at the scene. If the touched item is collected as possible evidence, Touch DNA analysis may be able to link the perpetrator to the crime scene. Touch DNA has been successfully sampled from countless items including weapons, vehicles, and clothing [2]. With the advent of more sensitive DNA typing kits, such as MiniFiler, Touch DNA profiles can now sometimes be obtained from bullet casings [3], documents [4], and latent fingerprints [5]. The aim of this article is to highlight the available sampling methods, provide recommendations for the collection of potential Touch DNA items at the crime scene, and to 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.