TUCSON, Ariz. — A murderer who died in a botched execution last week in Arizona was injected with 15 separate doses of a drug combination because the initial drug protocol of one dose didn’t seem to be enough to kill him, according to documents released late Friday by the state Department of Corrections to the inmate’s attorney.

The released reports are just the latest twist in the execution of Joseph Rudolph Wood III. Witnesses and his attorneys said Wood gasped and snorted for more than 90 minutes before he died, prompting the governor to order an investigation and reinvigorating a national debate over the death penalty.

Arizona Department of Corrections protocol calls for a prisoner to be executed with an initial dose of 50 milligrams of hydromorphone and 50 milligrams of midazolam but stipulates that more doses can be administered as long as the agency’s director gives the green light to do so.

That was the case in this instance, said Doug Nick, a Department of Corrections spokesman.

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Execution logs released to Wood’s attorney show that the initial experimental drug concoction wasn’t enough to kill him, leading officials to administer more drugs.

The second dose was administered at 2:08 p.m. and more doses were injected at a rate of almost every couple of minutes until Wood was pronounced dead at 3:49 p.m.

“The execution logs released today by the Arizona Department of Corrections shows that the experimental drug protocol did not work as promised,” said Wood’s attorney, Dale Baich.

The Department of Corrections refused to release a copy of the report to the Los Angeles Times but issued a statement defending the agency. “These records indicate the length of the procedure and the amount of drugs administered (for the execution) comply with the department’s mandate under state law,” the statement said.

Wood, 55, was sentenced to death in 1991 for the August 1989 shooting deaths of his estranged girlfriend, Debra Dietz, and her father, Eugene Dietz, in Tucson.

On July 23, Wood received an injection at 1:52 p.m. at the Arizona State Prison Complex in Florence.

It took so long for him to succumb that some witnesses to the execution counted several hundred wheezes before he was declared dead at 3:49, nearly two hours after the procedure began.

The incident comes in a year in which lethal injections had already triggered controversy over botched procedures and secrecy.

Wood had fought without success to get more information about the drugs and the expertise of his executioners.

His request, which was rejected by the U.S. Supreme Court, prompted one prominent appellate judge to call for the return of firing squads to carry out executions.