Arizona executioners injected Joseph Rudolph Wood with a lethal combination of drugs 15 times during the nearly two hours it took for him to die, according to documents released.

US death row inmates seek to halt executions Source: Associated Press

Wood's July 23 execution renewed debate over the death penalty and the efficacy of lethal injection.

It was the third execution to go awry in the US this year.

Arizona officials say Wood, who was convicted of a 1989 double-murder, never suffered and was completely sedated. His attorney says it was a "horrifically botched execution" that should have taken 10 minutes.

Records released to Wood's attorneys show he was administered the sedative midazolam and the painkiller hydromorphone in 50-milligramme increments 15 times, for a total of 750 milligrams of each drug.

He was pronounced dead after gasping more than 600 times while he lay on the table.

"Those are pretty staggering amounts of medication," said Karen Sibert, a longtime anesthesiologist and spokeswoman for the California Society of Anesthesiologists.

Sibert, an associate professor at Cedars-Sinai Medical Center, said patients who are sedated before a surgery typically receive no more than two milligrammes each of midazolam and hydromorphone.

"It would be rare that I would use more than two milligrammes even for a lengthy surgery," Sibert said. "If that is accurate, that is absolutely a lethal dose."

Wood's attorney, Dale Baich, said the dosage details show why an independent investigation of Wood's execution by a nongovernmental authority is necessary.

"The Arizona execution protocol explicitly states that a prisoner will be executed using 50 milligrammes of hydromorphone and 50 milligrammes of midazolam," he said in a written statement. "The execution logs released today by the Arizona Department of Corrections shows that the experimental drug protocol did not work as promised."