THE F.B.I. stunned the legal community on Monday with its acknowledgment that testimony by its forensic scientists about hair identification was scientifically indefensible in nearly every one of more than 250 cases reviewed. But the conclusion should come as no surprise to scientists. It is the culmination of a collision between law and science that began in 1989 in a Bronx courtroom with the murder trial of a janitor.
The case was the first to carefully evaluate the use of DNA fingerprinting. As a geneticist, I served pro bono as an expert witness for the defense. While prosecutors were dazzled by the potential of DNA technology to pinpoint perpetrators, the testing lab’s work proved to be shoddy and its conclusions unreliable. In a rare move, the scientific experts for both the prosecution and defense met and unanimously declared the DNA evidence unacceptable. The trial judge had little choice but to agree.
Shaken by the ruling, the National Academy of Sciences and the F.B.I. moved in the early 1990s to establish rigorous methods for DNA fingerprinting, which soon became the gold standard for forensics. The lawyers in the Bronx case, Barry Scheck and Peter Neufeld, went on to start the Innocence Project, which has used DNA as an objective lens to scrutinize past convictions. Such efforts have led to the exoneration or release of more than 300 people, including 20 who served time on death row.
As miscarriages of justice piled up, it became essential to understand precisely how the criminal justice system made such mistakes and how to prevent them. Troublingly, about a quarter of the cases examined by the Innocence Project (on whose board I now serve) involved forensic scientists who had erroneously claimed to identify defendants with near-certainty by matching hair samples, fibers, shoe prints or bite marks.