Physical evidence that is used to convict people in criminal cases is not always as reliable as the Illinois public has been led to believe. Hair analysis is one type of evidence that some attorneys and scientists believe is not definitive enough to put a person behind bars.
Hair analysis has been used in criminal cases for more than 150 years, with methods of examining and categorizing hair becoming increasingly sophisticated. The FBI published a manual on hair analysis in the 1970s and went on to train many people in state and local law enforcement. It was believed that a careful examiner could determine such things as whether the hair was human or animal and what part of the body it came from as well as say with some confidence whether it belonged to a specific individual. However, there has not been research to determine how common shared hair characteristics are, either across populations or on the body of an individual.
In 1999, independent experts hired by a federal government task force found just 4% of 150 cases were without problems regarding the hair analysis used to convict people. In 2015, the FBI looked at 268 convictions in which hair analysis was a factor and found that nearly all of them had issues. The analysis can be faulty for a number of reasons, including poor conditions in the lab or exaggerated findings. Faulty hair analysis was often used alongside other mistakes, such as unreliable witness testimony or false confessions, to convict individuals for felonies.
The public, juries and many people who work in law enforcement have been led to believe that such evidence as hair and blood spatter analysis are almost as reliable as DNA. However, studies increasingly show that these disciplines are actually junk science that can result in innocent people facing false convictions.