SODOM & GOMORRAH: Our culture’s lack of moral grounding has many consequences. One is how we treat uncertainty in criminal law, which has led to a blind obedience to the power of the confession and forensic science.
DNA and fingerprint evidence are largely considered solid evidence in most modern courts of law. The presence of one or both is usually enough to secure a conviction. Dr. Itiel Dror, a cognitive psycholgist at University College in London challenges us to consider an alternative. He has looked at DNA examiners’ interpretations of results and found there to be a strong bias in some complex cases. In 2009, America’s National Academy of Sciences used Dr. Dror’s previous work to point out that the claim of zero error rates in fingerprint cases was scientifically impossible.
Quite recently, Dr. Dror and Dr. Greg Hampikian, a forensic biologist at Boise State University have published a study in Science & Justice that reiterates the claim that DNA evidence may not be infallible. The two doctors gave DNA evidence from a real case to 17 DNA examiners in a government laboratory in the United States. The case was from a gang rape in Georgia in which one man testified against two others in exchange for a lighter sentence, even though all three denied any involvement. Original case investigators said that DNA indicated that one of the three was involved.
The original case workers knew the details of the case and knew that their tests were crucial to the outcome since Georgia requires evidence before a plea bargain is considered valid. However the researchers in the doctors’ experiment knew nothing about the case details. Four couldn’t say one way or the other if any of the three were involved. Twelve thought that the accused should be excluded. Only one said that the evidence supported involvement.
Dr. Dror and Dr. Hampikian suspect that the difference in prior knowledge skewed the results in the original case. Dr. Dror suggests that DNA evidence in approximately 25% of cases can be ambiguous due to tiny sampling or mixing material from more than one person. Cognitive bias appears to be a factor in forensic examinations, contributing to the perception that forensics is an infallible science.
It’s very easy to crave certainty when something tragic happens, especially when one is aware of the tragedy. It’s easy for this natural instinct for solid ground in a human dilemna to consciously or unconciously manifest itself as faith in the ability to find that certainty. The classics were able to accept uncertainty as inevitable; we, on the other hand, have been brought up to believe that we can find solid answers in science.