Still, without glaring new proof of innocence, courts have been reluctant to reopen cases based on even the most dubious of dental claims, leaving scores more defendants with questionable convictions to languish in prison or on death row, said Chris Fabricant, the Innocence Project’s director of strategic litigation.

One of them is Mr. Howard. His appeal cites the scientific consensus that bite-mark identifications are unreliable, and questions the methods used by Dr. West. The appeal to reverse his conviction, prepared by the Mississippi Innocence Project at the University of Mississippi, also cites newly completed DNA testing that found no traces of Mr. Howard on the murder weapon, the body or elsewhere at the crime scene.

Georgia Kemp, a reclusive 84-year-old in Columbus, Miss., had been stabbed to death and was partially dressed when police found her body among smoldering fires in her rundown house in 1992. The medical examiner found bruises “consistent with” rape but no hair or semen to prove it.

In the absence of fingerprints or witnesses, it was understandable when the police turned to Mr. Howard as a person of interest: Only four months earlier, he had gone to Columbus after spending most of the two previous decades in prison for attempted rapes.

But soon enough, an arguably shoddy process of justice began.

Mr. Howard had a history of mental illness and he made a series of seemingly incriminating, if contradictory and irrational, statements that made him the prime suspect. Though no confession was recorded or written down, he reportedly told one police officer that “the case is solved” and that “I had a temper and that’s why this happened,” even as he said that six others were involved and he failed to recognize Ms. Kemp’s house.

Three days after Ms. Kemp was buried, the medical examiner had her exhumed so that Dr. West could look for bite marks using a fluorescent light method he had developed. He said he found three bites and — without showing any photographs or other evidence — testified at trial that Mr. Howard was the biter “to a reasonable medical certainty.”

Image A mold of Mr. Howard’s teeth used to link him to the crime. Credit... Counsel for Eddie Lee Howard

Adding to the circumstantial evidence, Mr. Howard’s girlfriend said he had bitten her during sex and that he smelled like smoke the day after the murder.