Two men were separately convicted in the 1990s of raping and killing 3-year-old girls who lived several miles apart in Noxubee County, Mississippi. One was sentenced to die. Both convictions featured bite mark evidence which was later discredited, due to DNA evidence that pointed to a single killer who later confessed to the crimes.

The two convicted men, Kennedy Brewer and Levon Brooks, were released from Mississippi prisons in 2008, and filed federal lawsuits against the death investigators who had testified about the alleged bite marks on the bodies of the little girls that had led to the convictions.

The district court threw out the suits against Steven Timothy Hayne and Michael H. West, the forensic experts, claiming that they had immunity from such suits. But now a federal appeals court has again held that both experts are covered under “qualified immunity”—even though their testimony is now viewed as negligent.

“Plaintiffs have made a compelling showing that Defendants were negligent in their forensic analysis, but negligence alone will not defeat qualified immunity,” ruled the 5th Circuit U.S. Court of Appeals this week. “Viewed in its entirety and in the light most favorable to Plaintiffs, the record tends to show that Defendants were negligent—perhaps grossly so—but no more.”

Brooks was convicted in 1992 of the murder of Courtney Smith, the daughter his ex-girlfriend, according to court filings. The little girl had been sexually assaulted and drowned, and then found floating in a pond near her home in September 1990. The autopsy found two small contusions on the back of her right wrist which were identified as human bite marks. Hayne, a private pathologist who performed autopsies for Mississippi at the time, brought in the dentist West, who concluded the two small impressions were made by the perpetrator’s two front teeth. Dental impressions from 13 people of interest were taken, and West concluded Brooks had inflicted the marks, the records showed.

Brewer was convicted in 1995 of the murder Christine Jackson, his girlfriend’s daughter, whom he had been left in charge of on May 1, 1992, according to the documents. The girl had been raped and strangled, and her body was later found floating in a creek. Nineteen human bite marks made by the upper arch of the teeth were found on the girl’s body, West testified—and he connected them to Brewer, who was sentenced to die by lethal injection.

Four years later, Brewer was granted an evidentiary hearing on the DNA from semen found on Jackson’s body. That genetic profile matched Justin Albert Johnson, a convicted sex offender who confessed in 2008 to killing the girl. Just days later, Johnson also confessed to killing Smith, the other 3-year-old girl, court records showed.

Both Brewer and Brooks were released from prison in 2008, and filed separate federal lawsuits against the two experts. Although previous case law determined that private experts were not necessarily granted immunity in all cases, the district court ruled Hayne and West both were entitled to qualified immunity, since they were engaged in protected criminal investigative functions for the state.

The lawsuit contended both experts had “checkered” professional histories, by producing bite mark evidence with “extraordinary frequency,” especially in so-called “rape overkill” cases.

But the lawsuit did not prove “an intent to fabricate,” the appeals court has now ruled.

The biopsy examinations of the alleged bite marks were of utmost interest in the case. In the Brooks case, the biopsies showed no hemorrhaging, which indicated they were made post-mortem, according to the court documents. The Brewer case featured no such biopsies, and the plaintiffs alleged that Hayne didn’t do so as an effort to “deliberately (hide) exculpatory evidence.”

But the appeals court found that the documentation from the 1990s did not prove any such intent.

“Absent some additional evidence, the autopsy form and the result of the biopsy in the Brooks case are not sufficient to raise a reasonable inference that Dr. Hayne either deliberately failed to perform biopsies or withheld exculpatory evidence,” the three judges ruled.

Justin Albert Johnson was sentenced to life in prison without parole in 2012. The district attorney had intended to seek the death penalty for the two murders, but the girls’ families both requested authorities not to seek capital punishment. In his confessions, Johnson had not mentioned biting either of the victims, according to reports.

News of the appeal ruling was first reported by Radley Balko at The Washington Post—who has previously reported that Johnson was originally a suspect in the Courtney Smith killing in 1990s, but was excluded by West’s forensic examinations, leading the investigation to Brooks. West reiterated his belief in Brooks’ guilt in an April 2016 deposition on an unrelated case, The Post reported last year.

Both Brooks and Brewer have been formally exonerated and compensated under the terms of Mississippi’s wrongful conviction law, independent of their legal action against the forensic experts.