Enhanced forensic DNA recovery with appropriate swabs and optimized swabbing technique

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Enhanced forensic DNA recovery with appropriate swabs and optimized swabbing technique. / Hedman, Johannes; Akel, Yasmine; Jansson, Linda; Hedell, Ronny; Wallmark, Nanny; Forsberg, Christina; Ansell, Ricky.

I: Forensic Science International: Genetics, Vol. 53, 102491, 2021.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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Hedman, Johannes ; Akel, Yasmine ; Jansson, Linda ; Hedell, Ronny ; Wallmark, Nanny ; Forsberg, Christina ; Ansell, Ricky. / Enhanced forensic DNA recovery with appropriate swabs and optimized swabbing technique. I: Forensic Science International: Genetics. 2021 ; Vol. 53.

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TY - JOUR

T1 - Enhanced forensic DNA recovery with appropriate swabs and optimized swabbing technique

AU - Hedman, Johannes

AU - Akel, Yasmine

AU - Jansson, Linda

AU - Hedell, Ronny

AU - Wallmark, Nanny

AU - Forsberg, Christina

AU - Ansell, Ricky

PY - 2021

Y1 - 2021

N2 - Efficient sampling with swabs is crucial for optimal forensic DNA analysis. The DNA recovery is determined by the skill of the practitioner and the compatibility between the applied swab and the surface. Here we investigate the impact of swabbing technique and swab type on the DNA yield. Thirteen different swabs from four categories (cotton, flocked nylon, small foam and large foam) provided equal DNA yields for smooth/non-absorbing surfaces. Large foam swabs gave higher DNA recovery for an absorbing wood surface. Factorial design of experiments and ANOVA was applied to study swabbing techniques for cotton swabs. Two key factors for efficient sampling were found to be 1) holding the swab with an approximate 60° angle against the surface and 2) to rotate the swab during sampling. For absorbing wood, it was beneficial to wet the swab heavily. The results of the factorial experiments were used to develop swabbing protocols for different surfaces. When ten experienced practitioners sampled according to these protocols, the DNA yield was increased for ridged plastic (around 1.25 times more DNA) and absorbing wood (2.2–6.2 times more DNA). For window glass, representing a smooth/non-absorbing surface, sampling according to the protocol gave DNA yields equivalent to applying individual sampling techniques. The protocol lowered person-to-person variation for ridged plastic. In conclusion, we have developed instructive protocols for cotton swab sampling on three types of surfaces: smooth/non-absorbing, ridged/non-absorbing and smooth/absorbing. We believe that such swabbing protocols will streamline and simplify the training of new practitioners and improve sampling efficiency for invisible DNA residues in casework.

AB - Efficient sampling with swabs is crucial for optimal forensic DNA analysis. The DNA recovery is determined by the skill of the practitioner and the compatibility between the applied swab and the surface. Here we investigate the impact of swabbing technique and swab type on the DNA yield. Thirteen different swabs from four categories (cotton, flocked nylon, small foam and large foam) provided equal DNA yields for smooth/non-absorbing surfaces. Large foam swabs gave higher DNA recovery for an absorbing wood surface. Factorial design of experiments and ANOVA was applied to study swabbing techniques for cotton swabs. Two key factors for efficient sampling were found to be 1) holding the swab with an approximate 60° angle against the surface and 2) to rotate the swab during sampling. For absorbing wood, it was beneficial to wet the swab heavily. The results of the factorial experiments were used to develop swabbing protocols for different surfaces. When ten experienced practitioners sampled according to these protocols, the DNA yield was increased for ridged plastic (around 1.25 times more DNA) and absorbing wood (2.2–6.2 times more DNA). For window glass, representing a smooth/non-absorbing surface, sampling according to the protocol gave DNA yields equivalent to applying individual sampling techniques. The protocol lowered person-to-person variation for ridged plastic. In conclusion, we have developed instructive protocols for cotton swab sampling on three types of surfaces: smooth/non-absorbing, ridged/non-absorbing and smooth/absorbing. We believe that such swabbing protocols will streamline and simplify the training of new practitioners and improve sampling efficiency for invisible DNA residues in casework.

KW - Cotton swab

KW - Crime scene

KW - Foam swab

KW - Forensic DNA analysis

KW - Nylon-flocked swab

KW - Sampling

U2 - 10.1016/j.fsigen.2021.102491

DO - 10.1016/j.fsigen.2021.102491

M3 - Article

C2 - 33774569

AN - SCOPUS:85103127163

VL - 53

JO - Forensic Science International: Genetics

JF - Forensic Science International: Genetics

SN - 1878-0326

M1 - 102491

ER -