FILE - This undated file photo released by the Iowa Department of Corrections shows Gentric Hicks, an inmate at the Anamosa State Penitentiary in Anamosa, Iowa. Lawyers for Hicks, 74, maintain that he was wrongly convicted of first-degree murder in a 1976 slaying, but recent DNA testing on an orange hunting cap that the killer left at the crime scene was inconclusive and failed to exonerate Hicks.

IOWA CITY — Testing on a cap worn by the perpetrator of a homicide 45 years ago has failed to exonerate a prisoner who maintains his innocence, the latest setback for lawyers hoping to prove Iowa’s first wrongful conviction based on DNA.

Gentric Hicks cannot be excluded as one of two people whose DNA is believed to be on the orange hunting cap, according to recent court-ordered testing requested by Hicks’ lawyers. But the testing was inconclusive and could not examine Hicks’ late half brother, whom a key witness initially identified as the killer, because his DNA is unavailable.

Tricia Rojo Bushnell, director of the Midwest Innocence Project and one of Hicks’ lawyers, said she was disappointed but that she remained convinced Hicks is wrongly incarcerated and vowed to continue seeking his release, saying the focus would likely shift to requesting clemency.

Hicks is serving life without parole for the May 1976 slaying of 28-year-old Jerry Foster at the Hill Crest Motel near Fort Madison. He has been imprisoned for 45 years and works in the infirmary at the Anamosa State Penitentiary where two inmates used hammers to kill a nurse and a correctional officer in March. Hicks, 74, knew the victims and is devastated by their deaths, Bushnell said.

Iowa is one of 13 states that has never had a prisoner exonerated by DNA testing.

The Midwest Innocence Project and other lawyers have been reviewing old cases for potential miscarriages of justice and seeking court orders to conduct DNA testing on unexamined evidence. But tests conducted in at least five cases over the last two years have not turned up sufficient evidence to overturn a conviction, court records show.

Those include a 2000 Des Moines kidnapping in which not enough DNA was found on a gorilla mask worn by the assailant to draw any conclusions, and a woman’s 1985 homicide in Iowa City where there wasn’t enough evidence to point to alternative suspects. As in Hicks’ case, the testing also didn’t prove the guilt of people convicted of the crimes.

Bushnell said DNA testing in Iowa has been hampered by missing evidence, floods that destroyed evidence and an open records law that allows police to withhold investigative reports indefinitely. Another problem has been the degradation of skin cells on stored evidence, leaving analysts without enough material to develop full DNA profiles.

Hicks’ attorneys argued that his conviction was tainted by discredited fingerprint analysis, a mistaken identification by Foster’s mother, and a prosecution witness who got leniency for implicating Hicks.

A man posing as a hotel guest robbed Foster’s mother at gunpoint in the middle of the night, then shot Foster to death during a scuffle before fleeing. An accomplice detained by Foster’s father outside the motel initially told police that the shooter was his friend, Willie Jefferson, Hicks’ half brother.

Hours later, the accomplice changed his statement and said the shooter was Hicks, who was known to local authorities and immediately arrested. Officers never interviewed or investigated Jefferson, who died in the 1990s.

Lorraine Foster identified Hicks as her son’s killer after picking him out of lineups that did not include Jefferson. She used racial slurs when talking to police and described Hicks, who is Black, as having “the usual Black face.”

Hicks’ lawyers sought the testing after learning that a cap that came off the killer’s head during the scuffle had never been tested for DNA evidence. A crime lab examined the hat for hairs at the time but couldn’t find any, and it was kept in storage for decades at the Henry County Courthouse.

DNA analysts at Bode Technologies in Lorton, Virginia, developed a partial DNA profile from the interior rim of the hat. They found it was likely a mix of at least two individuals but that only one of them could be interpreted.

Comparing that profile to a sample from Hicks, the mixture is “at least 59 times more likely to be observed if it originated from Gentric Hicks and one unknown, unrelated individual than if two unknown, unrelated individuals,” their report concluded. The result provides “limited support” for implicating Hicks on a scale in which “strong support” is defined as at least 10,000 times more likely than not.