The National Registry of Exonerations recently issued its 2018 annual report. One hundred fifty-one people were exonerated in the U.S. last year after having been wrongfully convicted of various crimes ranging from traffic offenses to homicide. Together, the exonerees lost 1,639 years of their freedom.
Police and prosecutorial misconduct played an outsized role in convicting the people who were exonerated last year. In almost a third of the cases, a Chicago police sergeant and his officers were found to have framed the defendants for drug crimes and weapons offenses as part of an extortion scheme. Since the scheme was uncovered, dozens of defendants have been exonerated.
Official misconduct was documented in 107 cases, including 54 homicide cases, where the defendants were exonerated in 2018.
Another prominent feature of the 2018 exoneration cases was misleading forensic testimony, according to an analysis by the New York Times. For example, forensic analysts were found to have miscalculated or simply made up statistics about the certainty of the results of their tests. In one case, a consultant testified that "only one in a million" people could match a particular bite mark.
"A lot of the problem with forensic testimony is that the diagnosticity is overstated," said a law professor who authored the Registry's annual report. It sometimes "gets dressed up with this scientific certainty that isn't justified."
That's on top of the fact that many common forensic techniques lack sufficient scientific underpinnings. Even though these techniques are frequently used by investigators, many have been called into question by the National Academy of Sciences, the President's Council of Advisors on Science and Technology, and even the FBI itself. Examples of questionable forensic techniques include:
- DNA amplification
- Bite mark analysis
- Latent fingerprints
- Ballistics comparison
- Burn pattern analysis
- Footwear and tire tread analysis
- Microscopic hair comparison
In one of the cases that resulted in exoneration, a man was convicted of child abuse based on an exaggerated hair comparison analysis. Finding that there was a 1 in 2,700 chance that a particular hair belonged to the victim and a 1 in 48 chance that a second hair belonged to the defendant, the analyst inexplicably multiplied those numbers and concluded that there was a 1 in 129,600 chance that the hairs were random.
The analyst later acknowledged that the most he could have said scientifically was the first hair sample "could have come from the victim" and the second sample "could have come from the defendant."
In 2013, the FBI admitted that microscopic hair comparison is not scientifically valid. Untold hundreds of cases are being reviewed and may result in further exonerations.