Georgia on Tuesday postponed the scheduled execution of a two-time murderer as it prepared to use one drug instead of three for lethal injections of condemned inmates.
Warren Lee Hill, 52, was set to be executed on Wednesday for beating another inmate to death in 1990 while serving a life sentence for fatally shooting his girlfriend.
The state Department of Corrections said the execution would be delayed until Monday as Georgia switches from a three-drug cocktail that included the sedative pentobarbital to pentobarbital alone.
"The Department has been using pentobarbital in its execution process, and based upon the experience of other states and competent medical testimony, the drug has proven to be effective," corrections officials said in a statement.
Officials did not say what prompted the change. Pentobarbital is sometimes used to euthanize animals.
Hill's attorney, Brian Kammer, would not say whether he would file a legal challenge to the new protocol.
On Monday the Georgia Board of Pardons and Paroles rejected Hill's request for his sentence to be commuted to life in prison on the grounds that he is mentally disabled.
His lawyers now seek a stay of execution from the U.S. Supreme Court, which declined to review the case this year.
In March 2011, U.S. Drug Enforcement Administration agents took control of Georgia's supply of sodium thiopental, a sedative used in executions, after attorneys for several death row inmates said the state had improperly obtained the drug.
After the DEA seizure, Georgia replaced sodium thiopental with pentobarbital.
Texas, which executes more people than any other U.S. state, said this month it also would switch to using only pentobarbital in carrying out the death penalty after exhausting the usable supply of another drug.
The next execution in Texas is scheduled for Wednesday.
(Editing by Colleen Jenkins and Xavier Briand)