OKLAHOMA CITY — An inmate who writhed, moaned, and clenched his teeth before he was pronounced dead about 43 minutes after his execution began succumbed to the lethal drugs he was given, not a heart attack, after Oklahoma’s prisons chief halted efforts to kill him, an autopsy report released Thursday says.
The director of the Department of Corrections, Robert Patton, had said Clayton Lockett died from a heart attack about 10 minutes after he ordered the execution stopped. It hadn’t been clear whether all three execution drugs administered to Lockett had made it into his system, but the independent autopsy determined they did.
Southwestern Institute of Forensic Sciences at Dallas, which performed the autopsy, concluded the cause of death was ‘‘judicial execution by lethal injection.’’ But the report does not answer why the execution took so long and why Lockett writhed on the gurney.
Lockett’s attorney, David Autry, did not immediately return a call seeking comment. But Dale Baich of the Federal Public Defender’s office in Phoenix, who represents a group of Oklahoma death row prisoners who commissioned an independent autopsy of Lockett, said more information is needed.
‘‘What this initial autopsy report does not appear to answer is what went wrong during Mr. Lockett’s execution,’’ Baich said in a statement.
Oklahoma and other states have had problems in recent years obtaining lethal injection chemicals after major drug makers stopped selling them for use in executions. That has forced the states to find alternative drugs, purchased mostly from loosely regulated pharmacies that custom-make medications. Many states refuse to name the suppliers and offer no details about how the drugs are tested or how executioners are trained.
Oklahoma put executions on hold after Lockett’s April 29 execution.
Officials at Oklahoma State Penitentiary in McAlester have said Lockett’s vein collapsed during the injection. The autopsy does not say whether that’s the case, but confirms that medical technicians poked him about 12 times as they tried to find a vein before settling on one in his groin.
Governor Mary Fallin has ordered officials to review the events surrounding Lockett’s execution, including state execution protocols, which were changed in the weeks ahead of it. The Court of Criminal Appeals agreed to not schedule executions for six months. Three are set for November and December.
A spokesman for Fallin, Alex Weintz, said the autopsy report will be part of the full review. ‘‘We suspect they are in the final stages of that process,’’ Weintz said.
He said Fallin still supports the death penalty. ‘‘But we want our executions to be successful,’’ Weintz said, adding that Fallin asked the Department of Public Safety to recommend possible changes.
The autopsy report does not include any recommendations about the protocols.
A spokesman for the Corrections Department, Jerry Massie, said prison officials will have no comment until after public safety officials release their findings and recommendations.
To execute Lockett, Oklahoma used the sedative midazolam for the first time. The drug was also used in lengthy attempts to execute an Ohio inmate in January and an Arizona prisoner last month. Each time, witnesses said, the inmates appeared to gasp after their executions began and continued to labor for air before being pronounced dead.
Patton called for a complete ‘‘review/revision’’ of Oklahoma’s execution procedures following the Lockett execution, and said that he was willing to adopt protocols used by other states.
Among his concerns were that the state’s current protocol puts all responsibility and decision-making in the hands of the Oklahoma State Penitentiary’s warden. Patton, who came to Oklahoma from the Arizona Department of Corrections, did not specifically mention the drug midazolam or any other formula approved for use in the Oklahoma death chamber.
Lockett’s execution used a three-drug protocol: midazolam, vecuronium bromide, and potassium chloride. The state also has a protocol that would use midazolam with hydromorphone, the same combination used in the problematic executions in Ohio and Arizona this year.
A June lawsuit against the Department of Corrections on behalf of 21 Oklahoma prisoners alleged that prison officials are experimenting on death row inmates and violating the Constitution’s ban on cruel and unusual punishment.
The state says those claims are false.