Methods of examining the sexual assault patient are not standardized and a definition of what constitutes significant genital injury after sexual assault (SA) remains controversial. This pilot study tests the empirical validity (initial differential validity) of a genital injury severity scale (GISS) under development by the authors with the hypothesis that women who report SA have more severe external genital injuries than those who engage in consensual intercourse (CI). In this observational, prospective study, an initially developed GISS is applied and the exam results of 59 CI volunteers and 185 SA patients are compared. All examinations were performed by experienced sexual assault forensic examiners (SAFE) using toluidine blue (TB) and colposcopy. The Independent Samples Median Test indicates a significant difference in median genital injury type between CI and SA subjects (p < 0.0001). There is a significant difference in the prevalence of Class A (less severe) and Class B injuries (more severe) between the SA and the CI groups (SA: Class A 60%/Class B 40%; CI: Class A 90%/Class B 10% (p= 0.0001)). This initial validation study shows effectiveness in using magnification and TB, combined with a standardized injury severity scale, in describing external genital injury in women after sexual intercourse.