Good shedder or bad shedder—the influence of skin diseases on forensic DNA analysis from epithelial abrasions

Abstract

The successful analysis of weak biological stains by means of highly sensitive short tandem repeat (STR) amplification has been increased significantly over the recent years. Nevertheless, the percentage of reliably analysable samples varies considerably between different crime scene investigations even if the nature of the stains appears to be the same. It has been proposed that the amount and quality of DNA left at a crime scene may be due to individual skin conditions (among other factors). Therefore, we investigated DNA from handprints from 30 patients acutely suffering from skin diseases like atopic dermatitis, psoriasis or skin ulcer before and after therapy by STR amplification using the new and highly sensitive Powerplex® ESX17 kit in comparison to 22 healthy controls. Handprints from atopic dermatitis patients showed a correct and reliable DNA profile in 90% and 40% of patients before and after therapy, respectively. Regarding psoriasis patients, we detected full DNA profiles in only 64% and 55% of handprints before and after therapy. In contrast, in ulcus patients and controls, full DNA profiles were obtained in much lower numbers. We conclude that active skin diseases like atopic dermatitis or psoriasis have a considerable impact on the amplificable DNA left by skin contact with surfaces. Since up to 7% of adults in European countries suffer from one of these diseases, this could explain at least partially the varying quality of DNA from weak stains.

The complexities of DNA transfer during a social setting

“…These results support the hypothesis that some individuals may deposit more DNA than others when touching a surface [7,9,18] even though other factors such as differences in manner of contact [2,3] may also play a role. Another consideration is the size of the item in question.…”

Everything clean? Transfer of DNA traces between textiles in the washtub

“…without any known skin disease to exclude an influence as described by Kamphausen et al [17]. Samples were collected in 2012 and 2013 in the Institute of Legal Medicine, University Hospital Essen, Germany.…”

“…BExtrinsic^variables also were described such as different surface conditions and different manners of DNA application [19,20]. Besides nuclear DNA from keratinocytes [17], a recent study suggests Btrace DNA^to be derived from sebaceous glands [21]. All these studies investigated scenarios using more or less Bdry conditions^.…”

“…However, techniques have further developed and several authors suggest different variables influencing the amount of DNA left on surfaces [14][15][16]. Some Bintrinsic^variables qualifying the person as Bgood^or Bbad shedder^ [14] could be individual skin conditions, maybe altered by dermatological diseases [17], age [18], or gender. BExtrinsic^variables also were described such as different surface conditions and different manners of DNA application [19,20].…”

Prediction of people’s origin from degraded DNA—presentation of SNP assays and calculation of probability

“…DNA extraction from artificial stains was done by a modified phenol-chloroform method; DNA content from artificial stains was determined with the Quantifiler® Human DNA quantification kit (Applied Biosystems) as described before [19].…”