A Lancaster County grand jury found Friday that executed Nebraska prisoner Carey Dean Moore died of respiratory failure from toxicity from multiple drugs.
No violations of law in the death were found.
Moore, 60, was put to death on the morning of Aug. 14 for the 1979 murders of Omaha cab drivers Maynard Helgeland and Reuel Van Ness Jr.
The grand jury heard evidence and testimony Friday from Department of Correctional Services Director Scott Frakes, pathologist Robert Bowen of Omaha, State Patrol Investigator Stacie Lundgren and Lancaster County Sheriff's Capt. Tom Brookhouser.
A grand jury is required by state law when someone in law enforcement custody dies.
Moore, who was the first Nebraska condemned inmate executed in 21 years, was given four lethal injection drugs: diazepam, fentanyl, cisatracurium and potassium chloride. The procedure was unique in that the drugs had never been used in that combination to put a prisoner to death.
An autopsy report ordered in Moore's death was not made available Friday, but will be part of the record at a later time, said Lancaster County Attorney Pat Condon.
One controversy surrounding the execution was that about 15 minutes into the procedure, witnesses, including four members of the media, were blocked from observing for 14 minutes, which included about six minutes after Moore was pronounced dead. That hindered transparency and true reporting of the effects of the drugs.
Prison spokeswoman Dawn-Renee Smith said the department had planned to lower the curtain following the administration of the last drug.
A University of Nebraska Medical Center pharmacist, Ally Dering-Anderson, who had no connection to the execution, said later that week that Moore was probably dead two to three minutes after he got a high dose of fentanyl, more than 2 milligrams, which is generally considered fatal.
With that dose, he would not have been able to get enough oxygen to sustain life, she said.
Moore was originally sentenced to death in 1980 by electrocution, but avoided execution for 38 years, by which time the electric chair had been declared unconstitutional by the Nebraska Supreme Court. The Legislature then enacted lethal injection as the method of execution in Nebraska.
A dozen men remain on death row, including Jose Sandoval, convicted of killing five people in an attempted bank robbery in Norfolk. He has been notified by the Department of Corrections of the drugs that would be used in his execution, but has not received a death warrant.