DNA transfer through nonintimate social contact
Section snippets
Background
Forensic science has long since had an important role in the investigation of sexual offences. The identification of semen on intimate swabs taken from the complainant, together with DNA analysis to establish the possible source, has proven invaluable in such cases. Often the scientist is also asked to evaluate the findings and give an opinion of the significance of the results in light of the prosecution and defence accounts. Where the issue to be addressed relates to whether or not sexual
DNA transfer during nonintimate social contact—initial trial
Male participants took penile swabs from themselves following staged nonintimate social contact with a female and simulated urination, and the underwear the males were wearing at the time of the simulated urination was subsequently seized. DNA was recovered from the underwear, and DNA analysis of these samples together with DNA analysis of the penile swabs was carried out. The resulting DNA profiles were interpreted. This was an initial investigation to determine whether transfer and recovery
Results
Full details of matching female DNA detected in the underwear and penile swab samples for all of the trials are given in Table 1, Table 2, Table 3, Table 4, Table 5, Table 6, Table 7, Table 8, Table 9, Table 10, Table 11.
Discussion
It has been documented that female DNA is detectable on the penis of a male following sexual intercourse after a period of 24 h has elapsed [8], and the Faculty of Forensic and Legal Medicine Guidelines [9] recommend sampling the penis within 3 days of an act of alleged sexual intercourse. In this study, no matching female DNA was detected on any of penile samples taken 6 h after the staged nonintimate social contact events. Even when swabs were taken immediately following the staged contact,
Conclusion
In this study, it was not possible to replicate the high levels of female DNA transferred from sexual intercourse by nonintimate social contact. DNA matching a female’s DNA profile on the inside front of the suspect’s underwear with no front opening greater than 1000 rfu, and/or on penile swabs greater than 200 rfu, would be expected to provide support for an allegation of sexual intercourse, even if the male and female concerned were alleged to have had nonintimate social contact of the type
Acknowledgements
Many thanks to those staff from the member AFSP BFF organisations involved in carrying out this research and donating samples.
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Cited by (20)
A synthetic fingerprint solution and its importance in DNA transfer, persistence and recovery studies
2023, Forensic Science International: SynergyDNA profiles from biological trace material contained in underwear and toothbrushes
2022, Forensic Science International: Genetics Supplement SeriesEvaluative approach to semen transfer in a case of alleged sexual assault: A case study
2022, Science and JusticeCitation Excerpt :Where data sets of sufficient size are available and the case observed outcome has not been observed within this dataset, FSI takes the conservative approach of assuming a prior observation. For example, in a dataset of the inside front of male underwear (n = 44) no observation of DNA transfer via social contact was found [18]. FSI, when using this data, will assign a probability of 1/45 (0.02) of DNA transferring from social contact, assuming a prior observation.
Is it possible to predict the origin of epithelial cells? – A comparison of secondary transfer of skin epithelial cells versus vaginal mucous membrane cells by direct contact
2020, Science and JusticeCitation Excerpt :In this experiment we have seen that secondary transfer of epithelial cells is possible directly after contact, but that the number of samples where female DNA was detected, and the proportion, was significantly lower compared to samples collected after vaginal penetration. As postulated the results in this study differs to some extent from the results observed by Jones et al. [8], who only detected transfer of few female alleles in 4 out of 30 samples after skin contact, by only counting the number of female alleles in the DNA result. In this study female alleles were detected in 85 out of 99 samples and also to some extent as the major contributor based on further evaluations with Mx and DNA quantities.
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Formerly.