Australasian Science: Australia's authority on science since 1938

Pubic Microbes Finger Sex Offenders

Bacteria found in pubic hair could be used to trace a person’s involvement in sexual assault cases, according to a study published in Investigative Genetics.

Hairs are one of the most common types of trace evidence collected during forensic investigations, but the majority of those recovered from crime scenes contain insufficient amounts of human genetic material to carry out DNA profiling of suspects.

Not only did the study report that bacteria associated with pubic hair can distinguish between males, females and individual people, but it found that an individual’s pubic hair microbiota are transferred during intercourse, indicating its potential for forensic analysis in sexual assault cases.

“The transfer of bacteria between victim and offender, in rape cases, may provide a new way of linking the offender to the victim in instances in which no human DNA is transferred,” said lead author Ms Silvana Tridico of Murdoch University.

The small study collected pubic and scalp hair from seven individuals, two of whom were a cohabiting couple. Scalp hair showed fewer distinct varieties of microbe and appeared to be more influenced by common environmental microbes. In contrast, each individual’s pubic hair harboured distinct communities of microbe.

While the microbial communities on pubic hair generally remained individually distinct and consistent over the course of the study, after 5 months the cohabiting couple’s microbiota were more similar to each other than previously.

Interviews revealed that the couple had sexual intercourse 18 hours prior to the collection of their pubic hairs. This suggests that an exchange of microbes had occurred, which the researchers say bodes well for future forensic applications involving sexual crimes.