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The Use of Fluorescence to Differentiate between Semen and Commonly Applied Medicaments

Abstract 472 Poster Session III, Monday, 5/3 (poster 245)

Background: For children and adolescents who present to the Emergency Department after alleged sexual assault, the detection of semen on skin is important forensically and medically. The Wood's Lamp (WL), emitting UV light at 360 nanometers, has previously been reported to be useful in rape evaluations because of it's ability to cause semen to fluoresce. However, published data has shown that zero out of 42 physicians were able to differentiate semen from other medicaments using a WL; and furthermore, zero out of 29 semen samples fluoresced with a standard WL. This study was conducted to determine if physicians could better distinguish between semen and other products using an alternate light source. Methods: The attending physicians, fellows, and residents of the Pediatric Emergency Medicine (PEM) division and the Emergency Medicine (EM) division at a tertiary care center were given a questionnaire reviewing their previous training, frequency of sexual assault evaluations, and use of a WL in these evaluations. The participants then used an alternate light to try to distinguish between semen and 13 products that might be found on the perineum of a child, or adolescent. A small sample of semen and the other products were applied to a clean, white, cotton surface and allowed to dry. Results: 48 physicians (18 attendings, 6 fellows, 24 residents) participated in the study (33 male, 15 female). The participants were trained in Pediatrics (5), PEM (13), and EM (30). The average years of emergency medicine practice for all participants was 4.7 (0.5-15 years). 30% report having some formal training in the collection of forensic evidence. 44% evaluate more than 5 cases a year of sexual abuse and 10% evaluate 20 or more. 50% of physicians have used a WL for rape evaluations previously but only 16% report identifying semen in the past. In our sampling, 25% of physicians (7 PEM, 5 EM) successfully differentiated the semen from the other products using the alternate light. Of the 15 participants who reported formal training in forensic evidence collection, only 2 correctly identified the semen sample. The products most commonly mistaken for semen were a hand cream, Castille soap, and Bacitracin.

Conclusions: The identification of semen, even with a light source that causes it to fluoresce, is difficult, as there are other common creams, ointments and soaps which may confuse the examiner. Suspected semen specimens must be correlated with microscopic and chemical analysis. Also, medical personnel should have more training in forensic evidence collection.

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(Spon by: James G Linakis)

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Nelson, D., Santucci, K. The Use of Fluorescence to Differentiate between Semen and Commonly Applied Medicaments. Pediatr Res 45, 82 (1999).

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