Lawyers representing some of the 46 Duke University lacrosse players tested in connection with an alleged rape of a stripper said that the lack of matching DNA on or in the woman proves that no rape or sexual intercourse took place. The “CSI effect” has conditioned the public to expect irrefutable forensic evidence in such cases, but the truth may not be so simple, reports the Raleigh News and Observer. According to a U.S. Department of Justice study, DNA evidence from an attacker is successfully recovered in less than a quarter of sexual assault cases.
Typically, when a woman reports that she has been sexually assaulted, hospital workers collect a “rape kit” — samples of semen, blood, hair and pubic hair. If the attacker wears a condom, doesn’t ejaculate or penetrates the victim with a foreign object, semen or other sources of DNA are unlikely to be collected. “DNA is an extremely reliable form of evidence, when it’s there,” said Rich Rosen, a law professor and specialist in wrongful convictions. “In a lot of cases, there is nothing there, and often we don’t know why nothing is there.” Durham District Attorney Mike Nifong has said he thinks that an assault occurred and that any assailants might have used condoms.