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.
Highlights
Touch DNA, commonly known as trace DNA, is widely used in forensic DNA casework as it is an important tool to link suspects to crime scenes, especially when other types of biological evidence such as body fluids cannot be found
There was a significant difference between the three recovery techniques to collect touch DNA with cotton and nylon swabs from textured plastic (F 2,33 = 14.351, p < 0.001) (Figure 1)
The increased volume of wetting reagent on the nylon swab resulted in some of the DNA sample left on the surface (p < 0.001) (Figure 2)
Summary
Touch DNA, commonly known as trace DNA, is widely used in forensic DNA casework as it is an important tool to link suspects to crime scenes, especially when other types of biological evidence such as body fluids cannot be found. Touch DNA samples are challenging because of the many variables, such as surface type [5], collection devices [5,6], collection techniques used and environmental factors [79], that can impact the success of obtaining a good quality usable DNA profile. Cotton and nylon flocked swabs are commonly used to collect touch DNA from surfaces and a study by Alketbi and Goodwin [5] reported that cotton swabs (150C) and nylon flocked swabs (4N6FLOQSwabs®) were effective in collecting. This study aimed to test different techniques using cotton (150C) and nylon flocked (4N6FLOQSwabs®) swabs to recover touch DNA from non-porous surfaces. Four recovery techniques were investigated to test the influence of humidity on touch DNA recovery
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