In 2004, a New Jersey prosecutor announced that DNA had solved the mystery of who killed an eighth-grad girl who was raped, beaten and strangled 36 years earlier. The killer turned out to be someone else, says the Los Angeles Times. DNA has solved crimes once thought unsolvable, brought elusive murderers and rapists to justice years after their misdeeds, and exonerated the innocent. Still, it is becoming clear that genetic sleuthing also has significant limitations.
Although best known for clearing the wrongfully convicted, DNA evidence has linked innocent people to crimes. In the lab, it can be contaminated or mislabeled; samples can be switched. In the courtroom, its significance has often been overstated by lawyers or misunderstood by jurors. The rush to collect DNA and build databases has in some cases overwhelmed the ability of investigators to process the evidence and follow up on promising leads. Some labs have huge backlogs of untested evidence. In some cases, criminals who could have been caught have offended again. Debates have flared over civil rights and privacy, presaging possible constitutional challenges to DNA collection and storage. University of California Irvine criminology Prof. William Thompson, a leading authority on DNA laboratory error, says, “When you look at all the errors that have come to light around the world — and we’re only finding the tip of the iceberg — it really raises concerns about how many people you want to have in a database. There are certainly doubts in my mind whether I would want to be in one.”