Forensic science has revolutionized law enforcement and the criminal justice system. But is its accuracy as infallible as we’ve been led to believe? Vox’s investigative documentary False Positive explores the consequences of our unwavering belief in this popular practice.
The film explores a gruesome crime that took place in 1984. The battered body of a 63-year-old woman was found in a vacant lot north of Milwaukee. Investigators needed direction and contacted a forensic dentist to examine the bite marks left on the victim. As a result of his findings, a suspect was quickly arrested. A young man named Robert Lee Stimson was charged with the crime and stood trial for missing a tooth.
What the main players in this story don’t realize is that this new kind of science — using dental impressions to identify bite marks on crime victims — isn’t science at all. In fact, it’s never been tested before, and it’s not a quantifiable practice like DNA testing. According to the researchers, the margin of error was high, and there were too many unreliable variables at play when analyzing the results, including skin texture and bite depth.
However, these uncertainties were not discussed throughout the investigation and subsequent trial. The presence of an authority figure like a dentist can effectively remove most doubts, even if the expert’s findings are hasty, incomplete and unfounded. Law enforcement bowed to the expertise of dentists and failed to adequately review visual evidence on their own. In the end, the jury complied.
Because of the ambiguous nature of this pseudoscience, Stimson’s wrongful conviction was later overturned in 2009. He lost 23 years of his life due to scientific flaws and deliberate misinterpretation of the evidence.
False positives call for a more thorough investigation into bite mark identification and its effectiveness in high-stakes criminal investigations. Before that, countless others were at risk of false imprisonment. The film’s approach is neither dry nor academic; it is imbued with an urgency of activism.
