Optimization of Collection Techniques for Touch DNA from Fingerprints using Various Swabbing Solutions in Forensic Applications
Thomasma, Sarah Michelle
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There has been minimal research on how to best obtain DNA from human fingerprints, generally known as touch samples. Most forensic laboratories use the double swab technique, in which a surface is treated with a moistened swab followed by a dry swab, because it has been shown to recover more DNA from surfaces than the single swab method. However, this method has not been objectively studied using various solutions with the goal of maximizing DNA yields, as was the objective of the present study. Swabs moistened with water were compared to those moistened with laboratory or commercially available detergents, including Formula 409, Simple Green, sodium dodecyl sulfate (SDS), triton X-100, and tween 20. Fingerprints were deposited on smooth glass substrates and prints were swabbed. DNA was isolated using a standard organic extraction procedure, yields were quantified, and relative yields were compared. The ability to produce short tandem repeat (STR) profiles was then examined. Results showed that a greater amount of DNA from fingerprints could be recovered using solutions other than water. Further results demonstrated that significant differences existed among DNA quantities recovered from different subjects and also among DNA quantities recovered from specific fingers. Swabbing solution did not have an effect on STR quality; rather, it was the increased DNA quantity recovered during swabbing that increased STR profile quality. Most importantly, it was shown that detergents have the ability to enhance DNA recovery; therefore, they should be used during DNA collection to increase the possibility of human identification in criminal investigations.If you are not a current Kalamazoo College student, faculty, or staff member, email email@example.com to request access to this SIP.