How forensic failure in the courtroom costs lives

For a law enforcement officer, the only thing worse than a violent crime going unsolved is when the wrong man or woman is convicted. If an innocent person goes to prison, investigators stop investigating, and the guilty party is free to victimize again. 

We are now learning that wrongful convictions happen more often when junk science is allowed in court. And in at least nine cases, innocent people were put to death, all because faulty forensics were relied on to get a murder conviction. 

Science has an important role to play in America’s courtrooms. DNA, for example, which has been thoroughly vetted and tested, is highly reliable. A report by the National Academy of Sciences concluded no other forensic approach can link evidence to a specific individual with a high degree of certainty. Yet, unproven science is still routinely accepted as definitive evidence in America’s courtrooms.

For decades, expert witnesses told juries that a single strand of hair found at a crime scene could be compared to a suspect’s hair to prove his/her guilt. The use of microscopic hair comparisons dates back to the 19th century. For years, this type of testimony carried enormous weight in courtrooms, often presented as an objective, scientific fact. Jurors had little reason to question it, and based on expert testimony comparing hair samples, thousands of Americans may have been wrongly convicted.

In 2015, the FBI concluded that microscopic hair analysis testimony provided by its examiners was incorrect in at least 90 percent of the trial transcripts it reviewed. What had long been presented as reliable forensic evidence was, in many cases,........

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