Touch DNA Collection Techniques for Non-Porous Surfaces using Cotton and Nylon Swabs

Abstract

Touch DNA, commonly known as trace DNA, is widely used in forensic DNA casework. However, touch DNA samples are challenging because of the many variables that can impact the success of obtaining a good quality usable DNA profile. Cotton and nylon flocked swabs are often used to collect touch DNA from surfaces, so this study aimed to test different techniques using cotton (150C) and nylon flocked (4N6FLOQSwabs®) swabs to collect touch DNA from non-porous surfaces. There was a significant difference amongst the three recovery techniques tested to recover touch DNA with cotton swabs and nylon swabs from textured plastic (p < 0.001), with a nylon swab and 30μl of distilled water being more efficient than a cotton swab with 100μl of distilled water. There was also a significant difference between the four recovery techniques to recover touch DNA from glass surfaces exposed to high humidity and low temperature (5 °C/78%) (p <0.001), with a dry cotton or nylon swab being allowing more efficient recovery of touch DNA from non-porous humid surfaces such as glass.