OKLAHOMA CITY – An Oklahoma City man whose execution has been halted three times while legal questions about his mental health were debated is scheduled to be executed Tuesday night.

Garry Thomas Allen, 56, was last scheduled for execution in April when a federal judge issued a stay to consider appeals arguing that he is mentally ill and therefore not eligible for execution.

Thomas killed the mother of his two children on November 21, 1986, gunning her down in front of daycare workers after she arrived to pick up the couple’s 2 – and 6-year-old sons. Gail Titsworth had moved out of Thomas’ home four days earlier and rebuffed his pleas to return.

He was drunk and shot the woman four times before a police officer found him in a nearby alley and shot him in the face during a struggle over the officer’s gun.

Allen lost his left eye and sustained brain damage from the gunshot wound, according to court testimony, but a jury found him competent to stand trial.

Allen, who had a long history of drug and alcohol abuse and had been hospitalized for psychological problems, insisted on entering a “blind” guilty plea to murder, meaning the plea was entered without his knowing what his punishment would be.

His plea was intended to spare the emotions of his family and the family of the woman he killed, records show.

“I can’t see making a bad matter worse, bringing up the problems we were having and what motivated me to do what I did. It just makes things worse than ever,” he said, according to court transcripts.

Years of legal appeals focused on his mental competency. In 2005 a state pardon and parole board voted 4-1 to commute Allen’s death sentence to life in prison, but Oklahoma Governor Mary Fallin overruled the recommendation earlier this year.

Defense attorneys also have unsuccessfully raised claims that Allen’s mental health has deteriorated to such an extent during his years in prison that he no longer is eligible for the death penalty.

Unless a judge intervenes, Allen will become the fifth man executed in Oklahoma this year. The state’s executions are carried out by lethal injection.

(Reporting by Steve Olafson; Editing by Mary Wisniewski and Prudence Crowther)