Collection of forensic evidence from pediatric victims of sexual assault

To determine the time period after sexual assault of a child that specimens may yield evidence using DNA amplification. Secondary questions included the comparative laboratory yields of body swabs versus other specimens, and the correlation between physical findings and laboratory results.

Data from evidence-collection kits from children 13 years and younger were reviewed. Kits were screened for evidence using traditional methods, and DNA testing was performed for positive specimens. Laboratory data were compared with historical information.

There were 277 evidence-collection kits analyzed; 151 were collected from children younger than 10; 222 kits (80%) had 1 or more positive laboratory screening test, of which 56 (20%) tested positive by DNA. The time interval to collection was <24 hours for 30 of the 56 positive kits (68% positives with a documented time interval), and 24 (43% of all positive kits) were positive only by nonbody specimens. The majority of children with DNA were aged 10 or older, but kits from 14 children younger than 10 also had a positive DNA result, of which 5 were positive by a body swab collected between 7 and 95 hours after assault. Although body swabs were important sources of evidence for older children, they were significantly less likely than nonbody specimens to yield DNA among children younger than 10 (P = .002). There was no correlation between physical findings and laboratory evidence.

Body samples should be considered for children beyond 24 hours after assault, although the yield is limited. Physical examination findings do not predict yield of forensic laboratory tests.