In early December, we wrote that a number of common forensic tests used by law enforcement are being called "junk science" by the President's Council of Advisors on Science and Technology. The group issued a report noting that several tests used to convict people of crimes have not proven to be reliable enough to be considered scientifically valid.
Two of the tests identified as junk science are bite-mark analysis and microscopic hair comparison. In this post and our next post, we'll look at two real-life examples of how these tests have led to convictions that have since been overturned or called into question.
First, let's discuss what microscopic hair comparison is and is not. Individual hairs (such as those found at a crime scene) contain DNA that can be analyzed and potentially matched to a suspect. Such tests have proven to be reliable if done correctly. But that is DNA testing. Hair comparison, on the other hand, is little more than looking very closely at two samples of hairs and trying to determine visually if they look similar enough to be called a match.
In 1991, a North Carolina man named Timothy was convicted of the burglary and assault of an elderly woman. His conviction was based on flimsy evidence: testimony from three paid police informants and an analyst who claimed that Timothy's hair matched a sample from the crime scene. Other evidence that seemed to implicate someone else was ignored.
Timothy spent 25 years of a life sentence in prison before he was finally released in late 2015. His conviction was vacated and he is now a free man. The Innocence Project has been pushing prosecutors around the country to reexamine cases where convictions were based on microscopic hair comparisons, which has proven to be unscientific and highly unreliable.
Check back as we continue this discussion in our next post.