FILE - In this July 23, 2014, file photo, Arizona Republic justice reporter Michael Kiefer describes what he saw as a witness to the execution of Joseph Rudolph Wood, at the state prison in Florence, Ariz. Arizona officials said Monday, Dec. 22, that they are changing the drugs they use in executions after nearly two hours it took to execute Wood in July. (AP Photo, File)

TUCSON, Ariz. - Arizona officials said Monday they have been cleared of any wrongdoing in an execution this year that lasted nearly two hours, but they are nevertheless changing the drugs they use to put inmates to death.

According to a letter from Department of Corrections Director Charles Ryan to Gov. Jan Brewer, the department no longer will use the combination of midazolam, a sedative, and hydromorphone, a painkiller.

Instead, the agency will try to obtain pentobarbital or Sodium Pentothal, the powerful sedative also known as sodium thiopental that was used in lethal injections in Arizona until it became difficult to obtain.

Pentobarbital has been successfully used dozens of times in Texas, Georgia and Missouri but also is in short supply. Records obtained by The Associated Press show Texas has enough pentobarbital to carry out the first five lethal injections scheduled there in 2015.

If Arizona cannot acquire those drugs, it will use a three-drug combination that can include midazolam and potassium chloride, among others. That three-drug mix has been used successfully in eight executions in Florida, according to the report.

The July 23 execution of Joseph Rudolph Wood, convicted of murdering his ex-girlfriend and her father, Debbie and Gene Dietz, called into question the efficacy of the drugs used in Arizona after it took nearly two hours for Wood to die. He was given 15 doses of the drugs and gasped over and over before taking his final breath.

Wood's attorney, Dale Baich, says the execution was botched.

But results from an independent investigation conducted by a group of former corrections directors and experts found no protocols were broken and the state properly trained its execution team. The findings released Monday also show Wood was injected correctly but did not react to the drugs as expected.

The three-member team recommended the changes to the drugs used.

"The report is clear that the execution of inmate Wood was handled in accordance with all department procedures, which, as the report states, either meet or exceed national standards," Ryan said in a statement. "It was done appropriately and with the utmost professionalism."

But Baich was unsatisfied, saying the report failed to explain why the experimental drug protocol did not work as promised.

"The state should release all of the documentation and witness reports that went into this review," Baich said. "Only through discovery in a court of law will there be a truly independent and comprehensive examination of what went wrong during Mr. Wood's nearly two-hour execution."

The state has put on hold all executions pending the outcome of a lawsuit stemming from Wood's execution. Arizona has put 37 inmates to death since capital punishment resumed in 1992 and has about 120 inmates on death row.

The lawsuit was filed in June on behalf of Wood and other death-row inmates. It claims the inmates have a First Amendment right to know about specific execution protocols such as the types of drugs used in lethal injections and the companies that supply them.

The independent investigation reviewed drug combinations and other execution protocols of several states, including Ohio, Kentucky, Oklahoma, Texas and Missouri.

The investigators compared Wood's execution with that of Clayton Lockett in Oklahoma on April 29. The same sedative was used in both, but Oklahoma officials have said the catheters were improperly placed on Lockett, restricting the drugs' flow.

Lockett writhed, mumbled and lifted his head on the gurney during the 43 minutes it took him to die.

A federal judge ruled Monday that Oklahoma's lethal injection protocols are constitutional, and said the state can proceed with the scheduled executions of four death row inmates early next year.

The Arizona investigation found Wood did not feel pain. The lead doctor said he performed seven consciousness tests and found Wood was unresponsive. The doctor said he used a pin to prick Wood but got no response.

"The process and the implementation of the protocol was not 'botched' as has been described in the Lockett execution," the investigators wrote.

Pima County Medical Examiner Gregory Hess told investigators it's possible Wood was brain dead long before he died, and that gasps and snorting are "normal bodily responses to dying," according to the report. The autopsy findings in Wood's death have not been publicly released.

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News from © The Associated Press, 2014