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Int J Legal Med. 2018 Nov;132(6):1603-1609. doi: 10.1007/s00414-018-1839-z. Epub 2018 Apr 17.

Male DNA under female fingernails after scratching: transfer and persistence evaluation by RT-PCR analysis and Y-STR typing.

Author information

1
Department of Medical and Surgical Sciences (DIMEC), University of Bologna (Unibo), Unit of Legal Medicine, via Irnerio 49, 40126, Bologna, Italy. alessandra.iuvaro2@unibo.it.
2
Department of Medical and Surgical Sciences (DIMEC), University of Bologna (Unibo), Unit of Legal Medicine, via Irnerio 49, 40126, Bologna, Italy.
3
Laboratory of Molecular Anthropology, Department of Biological, Geological and Environmental Sciences (BiGeA), University of Bologna (Unibo), Via Selmi 3, 40126, Bologna, Italy.

Abstract

The collection of biological debris beneath fingernails can be useful in forensic casework when a struggle between the victim and the offender is suspected. In the present study, we set up a controlled scratching experiment in which female volunteers scratched the male volunteers' forearms, simulating a defensive action during an assault. A total of 160 fingernail samples were collected: 80 "control samples" before the scratching, 40 samples immediately after the scratching (t = 0 h), and 40 samples 5 h after the scratching (t = 5 h). The aim was to evaluate, using a real-time PCR approach and Y-STR profiling, the transfer and the persistence of male DNA under female fingernails after scratching. A significant reduction in DNA yield was observed between fingernail samples collected immediately and those collected 5 h after scratching, with a corresponding decrease in Y-STR profile quality. Overall, 38/40 (95%) of the fingernail samples collected immediately (t = 0 h) and 24/40 (60%) of those collected 5 h later (t = 5 h) were suitable for comparison and the scratched male volunteers could not be excluded as donors of the foreign DNA from 37 (92.5%) of the t = 0 h and from 10 (25%) of the t = 5 h profiles. The analysis of male DNA under female fingernails showed that Y-chromosome STR typing may provide extremely valuable genetic information of the male contributor(s), although 5 h after scratching the profile of the scratched male was lost in three-quarters of samples.

KEYWORDS:

Fingernail debris; Male/female mixtures; RT-PCR; Scratching experiment; Y-STR typing

PMID:
29666998
DOI:
10.1007/s00414-018-1839-z
[Indexed for MEDLINE]

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