A letter signed by 61 Oklahoma lawmakers – most of them pro-death penalty Republicans – has been sent to the state’s attorney general calling for a new hearing in the case of Richard Glossip, a death row inmate scheduled to be executed next month.

Forty-four Republican and 17 Democratic legislators, amounting to more than a third of the state assembly, have written to John O’Connor pleading for the new hearing.

The outpouring of concern is an indication of the intense unease surrounding the Glossip case, and the mounting fear that Oklahoma is preparing to kill an innocent man.

Glossip, 59, is due to be killed on 22 September as part of a sudden speeding up of capital punishment activity in Oklahoma. He was sentenced to death for the 1997 murder of Barry Van Treese, the owner of a Best Budget motel in Oklahoma City, where Glossip was manager.

Justin Sneed, the motel’s maintenance worker, admitted that he had beaten Van Treese to death with a baseball bat. But Sneed later turned state’s witness on Glossip, accusing the manager of having ordered the murder.

As a result, Sneed, the killer, avoided the death penalty and was given a life sentence. Glossip was put on death row almost entirely on the basis of Sneed’s testimony against him, with no other forensic or corroborating evidence.

In their letter, the 61 legislators ask the attorney general to call for a hearing to consider new evidence that has been uncovered in the case. Last year a global law firm, Reed Smith, was asked by state lawmakers to carry out an independent investigation.

Their 343-page report found that the state had intentionally destroyed key evidence before the trial. The review concluded that “no reasonable juror hearing the complete record would have convicted Richard Glossip of first-degree murder”.

Glossip’s scheduled execution forms part of an extraordinary glut of death warrants that have been issued by Oklahoma in recent weeks. In July, the state received court permission to go ahead with 25 executions at a rate of almost one a month between now and December 2024.

Should all those executions be carried out, Oklahoma’s current death row would shrink by almost 60% from its current occupancy of 43 prisoners.

The first scheduled execution of the 25 is that of James Coddington, 50, on 25 August. Coddington’s fate is now in the hands of Kevin Stitt, Oklahoma’s Republican governor, after the state’s parole board recommended that he commute the prisoner’s sentence to life without parole.

The clemency petition pointed out that Coddington had been impaired by alcohol and drug abuse starting when he was a baby. It said he had shown full remorse for having murdered Albert Hale, a friend who had refused to lend him $50 to buy cocaine.

Glossip is the second of the 25 death row inmates to be booked for execution.

The Republican-controlled state is rushing to kill so many prisoners over the next two years as it rebounds from a six-year capital punishment moratorium that was forced upon it following a spate of gruesomely botched executions. In April 2014 Clayton Lockett writhed and groaned on the gurney after lethal injection drugs were administered into his flesh rather than a vein – he took 43 minutes to die.

In January, 2015 Charles Warner was heard to say: “My body is on fire” as he was being killed. It was later discovered that the state had used an unauthorized drug in the procedure.

Glossip was set to be the next one to die in September 2015 but the execution was postponed after it emerged that the same mistaken drug was about to be used. Oklahoma halted executions for six years before the practice was cranked up again last October.

Remarkably, the first execution carried out after the hiatus in October 2021 was also botched. Witnesses saw John Grant displaying full-body convulsions and vomiting for 15 minutes.