A death row inmate in Oklahoma is making a last-ditch appeal for clemency ahead of his scheduled execution on 28 October.

John Marion Grant was sentenced to death for killing prison worker Gay Carter in November 1998 while serving sentences for four armed robberies.

If the execution goes ahead, he would be the first person put to death in the state since 2015.

Ahead of a planned clemency hearing on Tuesday, his attorneys say Mr Grant suffered years of abuse as a child in state institutions.

“John Grant never had a chance in life due to the severe abuse he suffered first at the hands of his mother and later in state-run institutions in Oklahoma whose horrific mistreatments are a well-documented scandal,” said attorney Sarah Jernigan.

“Yet he is deeply remorseful for his actions and has worked to redeem himself while incarcerated.

“We are hopeful that Oklahoma will give him a second chance by showing mercy, allowing him to live the remainder of his life in prison instead of being executed.”

According to reports of the abuse, children were routinely subjected to rapes, assaults and whippings in Oklahoma institutions.

Mr Grant’s attorneys say he was traumatised when he left the institutions and was jailed aged 17 for robbery.

The state had helped “create a broken man,” Ms Jernigan said.

On November 13, 1998, at the Dick Conner Correctional Center, Mr Grant “savagely and repeatedly stabbed” Ms Carter, a 58-year-old Correctional Food Supervisor.

Mr Grant murdered Ms Carter after she tried to end a personal relationship with him, the attorney said.

In August, Oklahoma’s new attorney general filed motions seeking execution dates for seven death-row inmates who have exhausted all of their appeals.