Sexual transfer of bacteria for forensic use

Transfer of bacterial species during sexual intercourse occurs despite condom use and could be used in a forensic setting, according to a study published in iScience.

Transfer of physical and biological material is a core tenet of forensic science. However, in crimes involving sexual assault that do not find human DNA transfer between victim and perpetrator, a criminal case can be hard to establish. Usually, this involves isolation of a perpetrator’s sperm from the victim (who is most commonly a woman). However, such samples need to be collected quickly, and the techniques used to identify DNA and differentiate it from that of the victim are limited. Differences in the microbiomes of the penile skin and vagina are due to the largely aerobic environment of the penis (apart from potentially under the prepuce of uncircumcised men), compared with the anaerobic vagina. These differences enable transfer of taxa not normally found in each area.