Wood's lawyers had filed an emergency appeal in federal court while the execution was underway, demanding that it be stopped. The appeal said Wood was "gasping and snorting for more than an hour."
The lawyers said the execution started at 1:52 p.m., but Wood continued to breathe and was alive an hour and 10 minutes later. Defense lawyer Dale Baich called it a botched execution that should have taken 10 minutes.
A message seeking comment was left with the Arizona Department of Corrections.
An Associated Press reporter witnessed the execution but could not immediately communicate with anyone outside the state prison in Florence where the execution took place.
Wood's case highlighted scrutiny surrounding lethal injections after two controversial executions, including that of an Ohio inmate in January who snorted and gasped during the 26 minutes it took him to die. In Oklahoma, an inmate died of a heart attack minutes after prison officials halted his execution because the drugs weren't being administered properly.
States have refused to reveal details such as which pharmacies are supplying lethal injection drugs and who is administering them, because of concerns over harassment.
Woods filed several appeals that were denied by the U.S. Supreme Court, including one on the basis that his First Amendment rights were violated when the state refused to reveal details of his execution such as the supplier of the drugs.
The Arizona Supreme Court also delayed the execution Wednesday morning to consider a last-minute appeal about whether Wood received inadequate legal representation at his sentencing. But about an hour later, the state's high court allowed the execution to proceed.
Wood argued he has a First Amendment right to details about the state's method for lethal injections, the qualifications of the executioner and who makes the drugs. Such demands for greater transparency have become a new legal tactic in death penalty cases.
The 9th U.S. Circuit Court of Appeals had put the execution on hold, saying the state must reveal the information. But the Supreme Court has not been receptive to the tactic, ruling against death penalty lawyers on the argument each time it has been before justices.
Wood's execution was Arizona's third since October and the state's 36th since 1992.
Wood was convicted in the 1989 shooting deaths of Debbie Dietz, 29, and Gene Dietz, 55, at an auto repair shop in Tucson.
Wood and Dietz had a tumultuous relationship during which he repeatedly assaulted her. Dietz tried to end their relationship and got an order of protection against Wood.
On the day of the shooting, Wood went to the auto shop and waited for Dietz's father, who disapproved of his daughter's relationship with Wood, to get off the phone. Once the father hung up, Wood pulled out a revolver, shot him in the chest and then smiled.
Wood then turned his attention toward Debra Dietz, who was trying to telephone for help. Wood grabbed her by the neck and put his gun to her chest. She pleaded with him to spare her life. An employee heard Wood say, "I told you I was going to do it, I have to kill you." He then called her an expletive and fired two shots in her chest.
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