Elsevier

Science & Justice

Volume 56, Issue 2, March 2016, Pages 90-95
Science & Justice

DNA transfer through nonintimate social contact

https://doi.org/10.1016/j.scijus.2015.10.004Get rights and content

Highlights

  • No matching female DNA was detected on the inside front of the 44 items of male underwear used in this research.

  • DNA transfer was found on the waistband and outside front of underwear worn by a male following non-intimate social contact.

  • Female DNA types were detected on 4 of the 30 penile shaft samples following non-intimate social contact.

  • No female DNA was found on any of the penile swabs collected following non-intimate social contact with a 6 hour time delay.

  • After unprotected sexual intercourse, full female DNA profiles were found on the male’s underwear and penile shaft swabs.

Abstract

The UK and Ireland Association of Forensic Science Providers' (AFSP) Body Fluid Forum (BFF) set out to assist in the interpretation of sexual offence cases where semen is absent on vaginal swabs but female DNA is present on penile swabs or male underwear, and the issue to be addressed is whether or not sexual intercourse occurred. This study aims to investigate the frequency and amount of female DNA transferred to the penis and underwear of males following staged nonintimate social contact with females and to compare the findings with the amount of female DNA transferred to the penis and subsequently to the underwear of a male who had engaged in unprotected sexual intercourse with a female. In this study, no matching female DNA was detected on the inside front of the 44 items of male underwear used in this research following staged contact of a nonintimate nature and subsequent secondary transfer to the penis. After sexual intercourse, full profiles matching the female participant were found on the inside front of the males underwear with maximum peak heights in the range between 1898 and 3157 rfu. It was possible to demonstrate that DNA can occasionally transfer to the waistband and outside front of underwear worn by a male following staged nonintimate social contact. Data obtained in this study suggest that a matching female DNA profile below a peak height of 1000 rfu on the waistband of a male's underwear might be explained by nonintimate social contact with secondary transfer of female DNA from the male's hands.

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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