Chicago (AFP) - The death penalty will resume in Nebraska for the first time in 20 years, with the US state planning to execute a convicted killer using a new, untested combination of drugs.
State prison officials on Thursday informed Jose Sandoval, on death row for the murders of five people during a 2002 bank robbery, of their intention to execute him by lethal injection.
The state intends to use a new drug protocol which could prompt legal challenges, and death penalty opponents quickly raised concerns.
"Any new combination of drugs means that the execution is a kind of human experimentation," Robert Dunham of the Death Penalty Information Center told AFP.
"That doesn't mean it won't work, but it raises another set of questions that prisoners will necessarily ask the court to address."
By law, officials can request Sandoval's death warrant be issued as early as two months after he was informed of the new drug protocol.
The state attorney general's office promised to defend against any legal challenges.
"Our office is obviously prepared to respond," spokeswoman Suzanne Gage told AFP.
If carried out, Sandoval's would be the first lethal injection execution in the midwestern state, which last put a prisoner to death in 1997 using the electric chair.
Like other states, Nebraska has struggled to find the medications it needs for lethal injections. Pharmaceutical companies have bowed to public pressure to stop providing the necessary drugs.
State officials did not disclose where they obtained their drugs for the new protocol, which avoids the use of the hard-to-get sodium thiopental as the primary anesthetic.
Danielle Conrad of the Nebraska chapter of the American Civil Liberties Union called the new protocol "an untested and experimental lethal injection cocktail."
"We are horrified," she said in a statement.
The new protocol consists of the sedative diazepam (commonly known by its brand name Valium), the powerful painkilling narcotic fentanyl citrate, the muscle-relaxant cisatracurium besylate, and potassium chloride, which stops the heart.
The death penalty has had a rocky history in the state. It was outlawed by legislators in 2015, but reinstated by voters through a 2016 ballot initiative.
Executions in the United States have declined over the last 10 years, with 23 carried out so far this year, according to the Death Penalty Information Center.