The New York Times created an awesome short documentary about the usage of hair in forensics and why that method was used to wrongfully convict more than 11% of cases where hair samples were used as proof. Using the new DNA sampling method in the 90s the FBI was able to get their hands on the correct perpetrator as the hair samples were not that accurate.
After DNA analysis was perfected and it became standard in FBI forensics, The Innocence Project has asked FBI to recheck the cases where people were convicted based on hair samples and, of those cases, 11% were wrongfully convicted and some of them were even on the death row.
From MY times:
Nationwide over the past 25 years, the project says, 316 people sent to prison have been exonerated through DNA analysis; 18 of them served time on death row.[…]In addition, the F.B.I. says it is examining more than 2,500 old cases that lacked DNA evidence, to determine if hair analysis, of itself, played a role in guilty verdicts. It is unclear how far along this review is.
This is heavy. In some of the cases DNA tests confirmed the verdict given based on hair samples, but there are still enough people who served time because they were the victims of… statistics. Hair samples can say that there is 1 in 10000 probabilities that you were at that place. 1/10000 might not seem much, but you could be trialed and get to jail because your hair would be pretty similar to someone else’s.
Read more on The New York Times.