Kevin Gannon, a retired detective sergeant with the New York Police Department, spent just 10 minutes looking at official documents related to the case of Rodney Reed — slated for execution in Texas on March 5 — before concluding that something was very, very wrong.

It was October 2014 and Gannon was working as part of a three-cop team featured on the A&E channel true-crime show Dead Again. The program follows the trio of veteran detectives as they reinvestigate old murder cases. The team approaches the cases cold, not knowing what original police investigators concluded — or who was arrested and prosecuted in the end. Sometimes, Gannon says, he and his colleagues end up agreeing with the official outcome. Sometimes, they do not.

In this case, the investigators were probing the 1996 murder of 19-year-old Stacey Stites in a rural town in Central Texas. Gannon was given the autopsy report, crime scene photos and video, and police reports. “The first thing I remember [thinking] is, ‘Oh my god, this is way off,’” he told The Intercept. I knew it was wrong.” He went to talk to his producer and, by 7 p.m. that night, was sitting across from Reed’s Innocence Project lawyer, Bryce Benjet. Today, Gannon is among a number of people who are convinced the state of Texas is preparing to execute an innocent man.

Gannon’s reinvestigation of the Reed case will be shown in Monday night’s episode of Dead Again. (Full disclosure: I was interviewed about my reporting by A&E.) At the same time, Gannon’s conclusions, along with those of three of the country’s leading forensic pathologists who have studied the case, are at the heart of a new appeal on Reed’s behalf, filed on Thursday, Feb. 12. The appeal argues that new scientific evidence proves conclusively that the state’s theory of the murder is “medically and scientifically impossible,” and that Reed is, in fact, innocent.

Specifically, Gannon and the forensic experts have concluded that the state’s timeline for Stites’ death is off by several hours. They contend that the decomposing of Stites’ body — observed in crime scene photos and video — prove that she was murdered at least four hours earlier than the state claims. Moreover, they conclude that she was likely killed somewhere far from where her body was found.

The findings are significant. Both the timeline and the location of the murder have been central to the state’s theory of the case since the beginning. What’s more, the new revelations contained in the defense brief point to a different man, a man who has long been suspected by Reed’s supporters to be the real murderer, and who was the source of the police and prosecutors’ timeline from the start. That man is Stites’ former fiancé, Jimmy Fennell, Jr., a rookie police officer at the time of her death, who testified that he was alone with Stites on the night before she was found murdered.

Reed’s lawyers are now asking Texas’ highest criminal court to stay his execution and overturn his conviction. Andrew MacRae, one of Reed’s attorneys, told reporters at a press conference last week, “Ultimately, we’re convinced that Mr. Reed will be found innocent if given a new, and fair, trial.”

STITES’ PARTIALLY-CLOTHED BODY was found just after 3 p.m. on April 23, 1996. She had been reported missing that morning after she failed to show up for a 3:30 a.m. shift at a local grocery store. Fennell’s truck, which she’d allegedly driven to work from her home in Giddings, Texas, nearly 30 miles away, was found in a high school parking lot roughly 10 miles from where her body was dumped.

Her murder went unsolved for nearly a year before cops, acting on a hunch, compared semen DNA found inside her to 29-year-old Rodney Reed, collected in connection with an unrelated, earlier case of alleged sexual assault. It was a match, and Reed was charged with Stites’ murder. The state claimed that he had somehow encountered and overpowered Stites as she drove to work that morning, then raped and murdered her, discarding her body in the woods. Although he initially denied knowing Stites, Reed eventually admitted that he had been having an ongoing, secret and consensual sexual relationship with Stites. The last time he had sex with her, he has said, was nearly two days before her body was found.

Aside from the fact that Reed is black and Stites was white — an interracial relationship that in a small Texas town could itself be dangerous — there was another reason Reed would not have revealed the affair: Stites was engaged to a white police officer, Jimmy Fennell. If exposed, the couple’s dangerous affair could become a deadly one.

Reed’s defenders have long maintained that Reed was set up by Fennell for his fianceé’s murder, likely after Fennell found out about the illicit relationship. In a recent article about the case, The Intercept chronicled Fennell’s history of violence, including allegations of stalking and rape. Indeed, Fennell is currently serving a 10-year prison sentence for kidnapping and sexually assaulting a woman while on duty and in uniform. That woman publicly revealed her identity to The Intercept for the first time in the hopes that she might save the life of Reed, who she believes to be innocent.

The new appeal seeks to fill gaps in the police investigation and trial defense that have haunted Reed’s case since the start. At trial, prosecutors argued that Reed’s DNA was the “Cinderella’s slipper” in the case, a direct link between Reed and Stites’ murder. Defense attorneys promised to show evidence of the affair, which would explain the DNA, but failed to call witnesses who could have done so.

In the new appeal, Reed’s lawyers offer affidavits from two of Stites’ grocery store coworkers who were never questioned by police about the murder. Both say they knew that Reed and Stites were in a relationship. Alicia Slater, who was still in high school at the time, says that while eating lunch together in the break room one day, Stites told Slater that she was having an affair with “a black guy named Rodney, and that she didn’t know what her fiancé would do if he found out,” Slater said in her affidavit. Slater said the exchange took place shortly before Stites was murdered. She did not tell police about the conversation because she wanted to leave Bastrop and was nervous about getting involved.

“I knew Jimmy Fennell was a cop and didn’t trust the police in Bastrop,” Slater said. “If I said something to accuse a police officer, I was afraid there would be repercussions for my family.” But after reading in November that Reed’s execution was imminent, Slater decided she had to come forward. She contacted Benjet.

The second coworker, Lee Roy Ybarra, told Reed’s lawyers that he had seen Reed and Stites together at the grocery store several times, behaving affectionately. But when Fennell would come in to visit Stites, he said, she would be a “nervous wreck” and would even “deliberately hide so that she didn’t have to talk to him.”

Even more damning for the state’s case — and for Fennell — are the medical affidavits at the center of the new appeal. According to three renowned forensic pathologists, Werner Spitz, Michael Baden and LeRoy Riddick, there is no way that Stites was killed in the early morning hours of April 23, as the state of Texas has always insisted.

Instead, they agree, Stites was killed well before midnight and then dumped in the woods early that morning. The pathologists explain that at death, blood no longer circulates and gravity leads it to pool under the skin in the lowest parts of the body. This becomes visible in the form of “lividity,” dark marks that resemble deep bruises on the skin. Stites was found on her back with her arms splayed above her head. But crime scene photos reveal widespread areas of reddish-purple lividity on the front of her body — on her face, right arm and hand, and chest. Lividity takes at least four hours to set. The pathologists say this means Stites was killed and then left for at least four hours in a position where she was slumped forward, with her one arm stretched out and down, before her body was abandoned in the woods.

The conclusions completely contradict the claims made by Fennell to police. Fennell says Stites left their apartment around 3 a.m. in order to drive to work. The night before, Fennell told police, he and Stites were together, alone in their apartment from 8 p.m. on. From the start, the state’s entire case has rested firmly on the timeline constructed by Fennell. Police never even searched the couple’s apartment.

The appeal contains more medical evidence to undermine Reed’s conviction. At trial, the Austin medical examiner, along with a crime scene analyst, asserted that the semen found inside Stites, which contained three intact sperm, had to have been deposited recently, within 24 hours of her death. This bolstered the state’s claim that Reed raped Stites just before her murder. But this trial testimony was scientifically inaccurate, say the forensic pathologists included in the new appeal. Not only can sperm remain intact inside the vaginal cavity for days, the fact that few sperm were found in this case actually supports Reed’s contention that he’d had sex with Stites nearly two days before she was found.

In fact, even Dr. Roberto Bayardo, the former Austin medical examiner who testified for the state at Reed’s trial, has recanted his original testimony. He says that his claims about the sperm were inaccurate and he could not actually pinpoint Stites’ time of death.

In sum, the doctors agree that the state’s case is untenable. “It is…my opinion, beyond a reasonable degree of medical certainty that, based on all of the forensic evidence, Mr. Reed is scheduled to be executed for a crime that he did not commit,” Michael Baden, former New York City chief medical examiner, said in his affidavit.

As the March 5 execution date nears, the case is now in the hands of Texas’ Court of Criminal Appeals. Reed’s lawyers are asking that the court grant a stay of execution in order to consider the new medical evidence. Reed’s lawyers are also appealing a lower court’s decision in November to deny Reed’s request for additional DNA testing in the case. The lawyers had asked that a judge order testing of never-before-tested items of evidence — including two lengths of a braided belt that the state says were used to strangle Stites. Attorney MacRae says he hopes the court will act quickly to avert an irrevocable miscarriage of justice.

“I would hope that the state would want to execute someone only after knowing” the person is actually guilty, he said. But in the Reed case, the state seems to want “to rush the execution date before we can get to the evidence of Reed’s innocence.”

For A&E’s Gannon,  the case against Rodney Reed is deeply unnerving — and the diminishing window of time left to right the wrong disturbing. After his own investigation, he says he is convinced not only that Reed is innocent, but also that he knows who is responsible for Stites’ murder. “For me, it’s obvious,” he said. “As far as I’m concerned, the murderer is Jimmy Fennell, the boyfriend. I can’t see it being anybody else.”

Dead Again airs on A&E at 9 p.m. Eastern, 8 p.m. Central. Watch a preview for the episode here.