Gunshot-residue evidence, used for years in thousands of investigations, is not so clear-cut as it has often been portrayed in court, or in the television crime dramas that have made forensics popular, says the Baltimore Sun. Across the country it is under increasing scrutiny as defense attorneys, prosecutors, and police officials evaluate how easily suspects’ hands can be contaminated by other items already covered in gunshot residue: handcuffs, car seats, even police officers themselves.
In Baltimore, prosecutors have begun a review of the way the evidence is used. Some agencies, such as the Boston police, have decided not to use it. “The ability to contaminate is the reason that there is such a limited degree of conclusions that can be made with gunshot residue,” said Marc S. Taylor, a gunshot-residue expert from California who has testified for both prosecutors and defense attorneys. There are serious questions about whether it is ever possible to avoid contamination with this type of evidence, particularly when, as in the case of the Baltimore Police Department, there is no monitoring to identify and prevent it, as would be standard in an independent laboratory. “People have been prosecuted and convicted on the basis of scientific evidence we know is flawed,” said Patrick Kent, chief of the Maryland public defender’s forensics division. “How can we make sure there’s justice in our system?” The Sun examines a case in which a man argues that he was convicted with flawed residue evidence.