Contrary to widely held beliefs, anogenital injuries are not exclusive to nonconsensual sex. In fact, the vast majority of injuries assessed during a medical-forensic examination are non-specific, meaning they could result from nonconsensual sexual contact (either with or without applied physical force) or from consensual sexual contact. This contradicts the often touted theory of human sexual response developed by Masters and Johnson almost 50 years ago. This theory holds that the normal physiological changes that occur during consensual sexual activity are protective against injury. These changes include lubrication, lengthening of the vaginal outlet, and pelvic tilt; and they are theorized to occur whenever there is mutual cooperation between sexual partners. According to this theory, the presence of anogenital injury would be more likely in situations in which the consensual sexual response did not occur, i.e., as in a sexual assault. Recent studies, however, have significantly undermined this theory in relation to anogenital injury. Generally, this theory should not be used as an explanation for the presence or absence of anogenital injury in sexual assault cases. Additional research is needed on such issues as the impact of skin tone on injury identification, the significance of location, the type and number of injuries, and the specific type of anogenital injuries in women who engage in consensual sex with other women, as well as anogenital injuries among men. Because of research gaps regarding the significance of anogenital injury in drawing conclusions about consensual versus nonconsensual sex, this paper discusses how prosecutors should use such evidence, as well as implications for other uses of injury evidence in a sexual assault case. 6 notes