FLORENCE, Ariz. (AP) -- The U.S. Supreme Court Tuesday declined to stop the execution of an Arizona death-row inmate hours before he was set to die by lethal injection for killing two people in a 1989 convenience store robbery.
The court's refusal to review a lower court's decision to deny a stay of execution cleared the way for Eric John King, 47, to be executed at 10 a.m. MST at the state prison in Florence.
He will be one of the last Arizona death-row inmates to be killed with a three-drug method before the state's planned switch to a single drug.
Defense attorney Mike Burke said he visited with King Tuesday morning.
"Although he's very calm, he continues to maintain his innocence," Burke told The Associated Press. "He's done what he can do. All he has left to do is maintain his dignity."
There are no further outstanding appeals.
Burke will witness the execution, partially to see that King doesn't experience pain, although Burke said that will be difficult because one of the execution drugs will paralyze him.
The Arizona Supreme Court declined to stay King's execution Monday after Burke argued that the state should wait until it enacts its new lethal injection protocol.
Corrections Director Charles Ryan announced Friday that Arizona will switch to using just one drug to allay any "perceived concerns" that sodium thiopental is ineffective, but that won't start until after the scheduled executions of King and Daniel Wayne Cook on April 5.
Burke had argued that the Department of Corrections may have engaged in fraud when it imported the sedative from Great Britain by listing it on forms as being for "animals (food processing)," not humans. Arizona Attorney General Tom Horne said the mislabeling resulted from a clerical error.
Arizona obtained the drug legally, and that's why it has been able to avoid problems other states have had, Assistant Attorney General Kent Cattani has said. Georgia's supply of sodium thiopental was seized by federal Drug Enforcement Administration agents on March 15 over questions about how it was obtained.
The drug is part of the three-drug lethal injection cocktail used by nearly all 34 death penalty states, but it became scarce last year after the sole U.S. manufacturer stopped making it.
Some states started obtaining sodium thiopental overseas, and lawyers have argued that potentially adulterated, counterfeit or ineffective doses could subject prisoners to extreme pain.
Texas and Oklahoma recently announced they are switching from sodium thiopental to pentobarbital in their three-drug protocol. Ohio has switched to using only pentobarbital for its executions, and Ryan said that's the drug Arizona might start using.
Burke said Monday that he was asking the U.S. Supreme Court to review the state court's denial of a stay, and a ruling was expected Tuesday morning.
Burke also was unable to successfully argue that King be granted clemency at a hearing Thursday. Burke had argued that the two key witnesses who testified against King at his trial have changed their stories, that no physical evidence exists and surveillance video used at trial was of extremely poor quality.
Vince Imbordino, a prosecutor with the Maricopa County attorney's office, argued that the photographic evidence was clear and that if jurors didn't believe King was guilty, they wouldn't have convicted him.
King was convicted of fatally shooting security guard Richard Butts and clerk Ron Barman at a Phoenix convenience store two days after Christmas in 1989. Butts and Barman both were married fathers whose families have testified that their deaths in a robbery that netted $72 devastated them.
Shortly before the killings, King had been released from a seven-year prison term on kidnapping and sexual assault charges. Police say King, who was 18 at the time, and another man kidnapped a woman and took her to an abandoned house, where both repeatedly and brutally sexually assaulted her over six hours.
Before he was sentenced in that crime, deputy adult probation officer Lee Brinkmoeller wrote that King had plans to reform himself.
"The defendant's plans for the future are to become a machinist and to have his own car, house, family, and start being able to do things for his mother for all the things she has done for him," Brinkmoeller wrote. "He states that he wants to have his mother be proud of him before she dies and he wants to be somebody."
Court documents show King had a troubled childhood. Born in a taxi on the way to the hospital in Phoenix, King was one of 12 siblings whose alcoholic, abusive and mentally disturbed father died of a heart attack when King was 11, according to court records.
Records also say King's mother struggled to provide for the children, who were so hungry at times that they tried to catch crawdads in irrigation canals and frequently were without electricity.
King reported to a prison psychiatrist that he had heard voices on and off his entire life, and suffered from anxiety and insomnia.
His son, 20-year-old Eric Harrison, saw King for the first time Thursday at the clemency hearing and asked the board to spare his father.
"This is the first time I've ever seen my dad, ever in life, and I know I love him," Harrison said. "That's my dad. He gave me life. Just don't take him."
Arizona has executed 22 death-row inmates with the three-drug lethal injection method since it began using lethal injection in 1993. The most recently was Jeffrey Landrigan on Oct. 26.
The state had previously executed 38 inmates with lethal gas since it started using that method in 1934. Another 28 inmates had been executed by hanging between 1910 and 1931.