Frequency of pubic hair transfer during sexual intercourse

This study measured the frequency of pubic hair transfer between a limited number of consenting heterosexual partners. The results derive from controlled experiments with a number of human subjects rather than forensic casework. Standardized collection procedures were observed, situational variables were tracked. Participants (forensic laboratory employees and their spouses) were six Caucasian couples who collected their pubic hair combings immediately following intercourse. Subjects provided informed consent in accordance with the protocol for human subjects approved by the U.A.B. institutional review board. The experiment was replicated ten times for five couples, and five times for another couple (total n = 110). Transfer frequencies were calculated from instances where foreign (exogenous) hairs were observed. Results showed at least one exogenous pubic hair in 17.3% (19/110) of combings. Transfers to males (23.6%, or 13/55) were more prevalent than transfers to females (10.9%, or 6/55). Only once were transfers observed simultaneously between both male and female. A total of 28 exogenous pubic hairs were identified. Subjects reported intercourse duration of 2-25 min, intervening intervals of 1-240 h, pre-coital bathing intervals of 0.25-24 h, and predominantly missionary position (76%). No clear relationship among these other survey variables was observed. The prevalence of female-to-male pubic hair transfers suggests the importance of collecting pubic hair combings from the male suspects as well as from female victims, provided the time interval is not extreme. Even under these optimum collection conditions, pubic hair transfers were observed only 17.3% of the time.