(Getty Images)

Alfred Swinton was just released from prison after serving 19 years. Swinton was first arrested shortly after the 1991 murder of Carla Terry in Connecticut. From the Innocence Project, which represented him:

He was arrested for the murder after police conducted a search of the basement of the apartment building where he lived and recovered a bra in a box in a common area that contained other clothing and objects. In addition to the bra, which the state theorized belonged to the victim, the state presented bite mark analyst Dr. Lester Luntz at a probable cause hearing who claimed that bite marks on the victim’s body were linked to Swinton.  The court concluded that the evidence was insufficient to establish probable cause and Swinton was released.

The case went cold for several years, until October 8, 1998, when Swinton was again charged with the murder. At the subsequent probable cause hearing, the victim’s sister, who had not identified the bra in 1991, changed her testimony, claiming she had given it to the victim on the night she was murdered. The state also presented a new bite mark analyst, Dr. [Gus] Karazulas, who testified – based upon a reasonable degree of scientific certainty – that Swinton “caused the bite mark that is depicted in the photographs” of the victim’s breasts, and that he was able to identify that the injury was inflicted “just before or at the time of death.” Based on this new evidence, the court found probable cause to charge Swinton of murder.

Recent DNA testing on saliva taken from the bite as well as from scrapings under the victim’s fingernails both excluded Swinton. He is now the 29th person since 2000 convicted or arrested based on bite mark evidence who was later exonerated.

Notably in this case, two expert witnesses claimed the bite marks were consistent with or a match to Swinton. (To his credit, Karazulas has since recanted his testimony.) I don’t doubt that either expert truly believed in their respective conclusions. But that both could be so wrong — and with such dire consequences for an innocent man — shows just how malleable and subjective the pattern matching fields of forensics can be. When the police come to you with a bite mark and the dental mold of their chief suspect, it isn’t at all difficult to see how someone practicing in such a subjective field could see similarities where none exist, even if their motives are completely pure. Cognitive bias is a powerful pollutant even in the more objective fields of forensics.

Finally, this is the part of the post where I point out that not only do prosecutors around the country continue to use and defend bite mark testimony, but also, to date, not a single court in the United States has upheld a challenge to its scientific reliability.