DNA is the “gold standard” in forensic science. Unlike bite marks, fingerprints, and hair, DNA is unique to each individual. Single-source DNA analysis compares alleles at each locus in the DNA from the crime scene with DNA in a large database to determine a match. DNA analysts also calculate a “Random Match Probability” that gives the probability that a randomly chosen person from the reference population would have the same DNA profile found in the evidence sample. In other words, an error rate for each match. DNA analysis is different from other forensic disciplines lack the availability of a sufficient database and error rates. 

 

That is why when a DNA analyst placed 16-year-old Josiah Sutton as the “perfect match” to the man who had kidnapped and raped a 41-year-old woman (who also identified him as the assailant), apart from Sutton's family, no one had any reason to think a mistake had been made. DNA didn’t lie. Thus, in 1999, Sutton and another teenager were sentenced to 25 years in prison. 

 

Despite the foundational validity of DNA analysis as a science, this discipline is not infallible. Humans can still make errors, which is exactly what was happening in the Houston, Texas crime laboratory where Sutton’s DNA was tested. 

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In 2002, a tip from a whistleblower exposed the ceiling leaks, underfunding, poorly trained employees, and the carelessness plaguing the crime lab.

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Hundreds of DNA samples were incorrectly interpreted, including Sutton’s.

 

When Sutton’s mother heard about the scandal on the news, she immediately contacted reporters, asserting her son’s innocence and securing him the opportunity to have his DNA retested. After four and a half years, Sutton was finally freed. Houston’s crime lab provides one example of why it is important to approach all forensic disciplines with a healthy dose of skepticism. While science does not lie, humans using science are susceptible to mistakes.

 

Or, in the words of Sutton’s mother,

 

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“DNA is science. You can’t blame DNA. You can only blame the people who used it wrong”.

 

 

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And science used wrong can cost someone their freedom, and even their life.