Video image of genital melanosis provides strong evidence to support identification of a sexual offender.

A man in his thirties was suspected of committing a sexual offense against a young girl. A video on his mobile telephone provided the only evidence. Photographs obtained from the video showed male genitalia in two views, with the penis in both views exhibiting unique pigmentation. We appraised this case with the cooperation of dermatologists, who diagnosed the pigmentation as male genital melanosis, a relatively rare disease, which matched that on the suspected perpetrator's penis. Photographs obtained from the video were thus decisive evidence of sexual offense and identified the perpetrator.