A Prince George’s County jury would not convict a man accused of stabbing his girlfriend to death because a half-eaten hamburger, recovered from the crime scene and assumed to have been his, was not tested for DNA. In Washington, a jury deadlocked recently in the trial of a woman accused of stabbing another woman because fingerprints on the weapon did not belong to the suspect. An Alexandria jury acquitted a man on drug-possession charges in part because a box containing 60 rocks of crack cocaine that he was accused of tossing from his car during a traffic stop was not tested for fingerprints.
Prosecutors say jurors are telling them they expect forensic evidence in criminal cases, just like on their favorite television shows, including “CSI: Crime Scene Investigation.” In real life, forensic evidence is not collected at every crime scene, either because criminals clean up after themselves or because of a shortage in resources. Yet, increasingly, jurors are reluctant to convict someone without it, a phenomenon the criminal justice community is calling the “CSI effect.” The shows have had an effect on courtrooms nationwide, according to lawyers, judges and jurors. Some prosecutors are calling experts to the witness stand simply to explain to juries why forensic evidence might be absent. And defense lawyers are exploiting the lack of scientific proof to plant doubt, even when there are eyewitness accounts, confessions or other compelling evidence.