Richard Glossip is intimately acquainted with the cell in Oklahoma state penitentiary known as “LL”. He’s been inside its 8ft by 12ft grey walls three times, waiting to be taken to the room next door – the death chamber.

Glossip was brought into the cell each time at 3am on the morning of his scheduled execution. In a letter and phone call with the Guardian from death row in McAlester, Oklahoma, last week, he described what it was like spending what he thought were his final few hours inside LL as the clock ticked down.

“One side of the cell is covered in bright lights that never go off, like you are out in the sun,” he said. “You are watched by cameras as well as a guard who sits outside your door 24/7.”

As Glossip’s date with death grew closer, guards started holding mock executions. They would lead an actor dressed in prison uniform into the death chamber, strap him on the gurney and then role-play the execution procedure from start to finish.

The entire dress rehearsal was carried out in Glossip’s full view. “I could see everything. I could have stayed in the back of the cell and tried not to watch, but I didn’t because I knew I was next.”

The most recent time Glossip was in cell LL was on 30 September 2015. “It was the hardest day of my life,” he said.

He remembers shivering in his boxer shorts, pacing up and down to keep warm in the cell which was cold as a meat locker. He repeatedly asked the guards what was happening, and could he talk to his attorney.

No idea, and no, they replied.

“The execution team was supposed to come and get me within 15 minutes and take me in [to the death chamber]. But nobody came. I paced and paced, prayed harder than I ever have. ‘Please God, stop them from doing this to me’.”

Two hours after his scheduled execution time, a man in a suit entered LL and told Glossip that he had been granted a stay. “It was like the heaviest weight had been lifted off of me,” he said. “My prayers were answered.”

The euphoria the prisoner felt after each of his three executions were temporarily called off didn’t last long. Not when a state as relentless in its pursuit of capital punishment as Oklahoma was out to get him.

He was sentenced to death for the 1997 murder of Barry Van Treese, owner of a Best Budget motel in Oklahoma City where Glossip worked as manager. No one has ever accused him of actually killing Van Treese.

Rather, Justin Sneed, a maintenance worker at the motel with a methamphetamine habit, confessed that all on his own he beat Van Treese to death with a baseball bat. Sneed later turned state’s witness and testified that Glossip had ordered the murder.

On the strength of Sneed’s testimony, with no other forensic or corroborating evidence, the state secured a death sentence for Glossip while the sole killer, Sneed, was given life without parole. Glossip, who went through two trials in 1998 and 2004 and was convicted twice, has always pleaded innocence.

In August, Oklahoma’s governor Kevin Stitt granted Glossip another reprieve, ordering a 60-day stay to give the courts time to consider new evidence. The postponement came just a day before the prisoner was due to be put back into “death watch”, the month-long formal countdown which ends with him being put in cell LL.

Now the whole grim process is starting up again. A new execution date has been set and unless something dramatic happens Glossip, 59, will before long find himself once again back inside LL at 3am, watching the clock tick down.

It’s a prospect that leaves his lawyer, Don Knight, profoundly troubled. He is distressed that his client has been brought so close to execution multiple times, likening the trauma to the way Islamic State has taken hostages to be beheaded and then called off the killing only to repeat it the following day.

“That’s where we are, we’ve fallen that low,” Knight said.

The lawyer is also deeply concerned about Glossip because he is convinced that an innocent man is facing imminent execution. Knight has been involved in about 50 capital cases and for him, the Glossip case stands in a league of its own.

“From the very first moment I saw this case, it never made any sense,” he said in an interview. “It was blatantly obvious to me, from the start, that this was a bad prosecution.”

Last year the global law firm Reed Smith was invited by state legislators to take a close look at the Glossip conviction. They produced a 343-page report which revealed a spate of alarming deficiencies in the prosecution.

The firm discovered that the police investigation into Van Treese’s murder had been glaringly mishandled. Sneed, the sole killer and the state’s star witness, had been contaminated – he only implicated Glossip as the mastermind behind the murder after detectives invoked the motel manager’s name six times during the interrogation.

Reed Smith revealed that critical physical evidence and financial documents had been destroyed by prosecutors before Glossip’s trial – a gross violation of legal process – while other evidence that could have transformed the case was never presented to the jury. The firm concluded that “no reasonable juror hearing the complete record would have convicted Richard Glossip of first-degree murder”.

Since the Reed Smith report was released in June, an avalanche of new information has been obtained casting further doubt on the conviction and death sentence.

Investigators found a handwritten letter from Sneed to his defense lawyer dated 2007, three years after the killer’s testimony at trial sent Glossip to death row. “There are a lot of things right now that are eating at me. Somethings I need to clean up,” he wrote. “I think you know were (sic) I’m going it was a mistake reliving this.”

Fresh doubt about the Sneed’s reliability as a witness has surfaced in the past two weeks. Reed Smith has put out new findings that show that he discussed “recanting” his testimony with several people over an 11-year period.

The most powerful new evidence points to allegedly improper communications between the lead prosecutor at Glossip’s trial, Connie Smothermon, and Sneed’s lawyer Gina Walker (who died in 2020). Lawyers for Glossip argue this was a breach of sequestration – the rule that prevents witnesses hearing what other witnesses say to avoid tainting their testimony.

Documents disclosed by the state attorney general last month contained email exchanges between Smothermon and Walker. In them, the prosecutor raised concerns about a specific aspect of Sneed’s testimony – a knife.

Sneed had told police that he was the only person present when he battered Van Treese to death. He also insisted that he had not used a knife in the attack.

Yet on 25 May 2004 the medical examiner at Glossip’s trial, Dr Chai Choi, told the jury that the victim had puncture wounds on the body and that these amounted to a “stabbing type injury”. A knife was found underneath Van Treese’s corpse.

How could Van Treese have cuts on his body when Sneed was the only attacker but did not use the knife? According to Reed Smith investigators, Smothermon sent an email to Sneed’s lawyer on the same day as Choi’s testimony.

“Our biggest problem is still the knife,” the prosecutor told Walker. “The victim and Justin both have ‘lacerations’ which could be caused from fighting / falling on furniture with edges or from a knife blade.”

She ended the email on a note of urgency. Referring to Sneed, she said: “We should get to him this afternoon.”

The next day, 26 May 2004, Sneed addressed the jury at Glossip’s retrial. He now told a very different story, saying that did indeed stab Van Treese in the chest.

“It now appears that Sneed tailored his testimony on the use of the knife,” Reed Smith concluded.

Unreliable star witness, incompetent police investigation, destroyed evidence, manufactured testimony – the list of flaws in the prosecution case grows longer by the day. “The whole thing from Walker and Smothermon, and Sneed’s changed testimony, it disgusts me,” Knight said.

Justin Humphrey, a Republican legislator in Oklahoma, used even sharper words. At a press conference to reveal the new evidence last month, he introduced himself as a “strong proponent of the death penalty”.

Then he addressed the prosecutors who had secured Glossip’s death sentence on seemingly shakey grounds: “You put a person on death row, you are looking at taking a person’s life. Which makes you no better than a murderer to me – why would you do that? Why would you manufacture evidence?”

The Guardian invited Smothermon, now teaching at the University of Oklahoma, to comment but she did not immediately respond. In a statement, Oklahoma’s current attorney general John O’Connor said that he had seen “no evidence” of Glossip’s innocence.

“It is disappointing that Glossip’s supporters are criticizing law enforcement, prosecutors, juries, and judges in an attempt to distract the public from the evidence beyond a reasonable doubt of Glossip’s guilt,” O’Connor said.

Glossip now has two petitions before the Oklahoma court of criminal appeals calling for a new evidentiary hearing.

Knight said that what has happened to Glossip should worry all of us. “This is what happens when the state is allowed to run amok. They can convict anybody of anything. And that’s what happened here. They poured their resources on top of an ordinary guy to show what they could do. And when that’s the case, none of us are safe.”

Glossip has been given a new execution date: 8 December. “The clock is ticking again. I can feel it,” he said.

On two separate occasions, he was offered a plea deal that would have taken him off death row and given life without parole instead. Both times he declined; he was not prepared to plead guilty to something he says he did not do.

“Innocent is innocent, period,” he wrote to the Guardian.

I asked him during the prison phone call whether he would regret making that decision were he to find himself, on 8 December, back in cell LL.

“I mean yes,” he said. “I still believe that innocent is innocent. You fight again.”

Whatever comes?

“Whatever comes,” he said.