Deduction of the order of sexual assaults by DNA analysis of two condoms

Differential DNA extraction procedures were performed on two condoms found at a rape scene. One of the condoms was recovered intact (A), while the second condom (B) had apparently ruptured during the alleged attack. Two related suspects (cousins 1 & 2) were identified as the potential semen donors. Condom B contained DNA from the female and from one of the suspects. Condom A contained DNA from the suspect identified on condom B and from an unidentified individual. The presence of DNA from suspect 2 on both condoms led to the deduction that his sexual activity preceded that of the unidentified suspect. The ability to determine such a sequence of events using DNA typing is unusual.