LAWYERS for a convicted double-murderer whose lethal injection in Arizona dragged on for two hours, while witnesses watched him gasping for breath and attorneys scrambled to halt the process, have called for a review of the "horrifically botched execution".

The ordeal in putting Joseph Wood, 55, to death on Wednesday at a prison southeast of Phoenix marked the third instance this year of a lethal injection gone awry, after mishaps in Ohio and Oklahoma that renewed the US debate over capital punishment.

Dale Baich, one of Wood's lawyers, who watched the execution and tried in vain to stop it, said: "He gasped and struggled to breathe for about an hour and 40 minutes." He called for an independent inquiry.

State Corrections Director Charles Ryan disputed suggestions Wood, who shot dead his ex-girlfriend and her father in 1989, had suffered.