The State of Ohio executed a convicted killer this morning using an untested method of lethal injection that no other state has ever employed.
Kenneth Biros was pronounced dead at 11:47 a.m. Tuesday, about 10 minutes after a lethal single-drug dose of an anesthetic was administered into his veins. The process had been expected to take as long as 30 minutes under the new technique.
The execution of Biros, who was convicted of killing and dismembering Tammy Engstrom in 1991, marks the first time a single drug has ever been used in an execution by lethal injection.
Before dying, Biros apologized for his crime and thanked his family for their support.
"Sorry from the bottom of my heart," he said. "My father, now I'm paroled to heaven. I will now spend all of my holidays with my Lord and Savior, Jesus Christ. Peace be with you all, amen."
Earlier Tuesday, the U.S. Supreme Court turned down Biros' last-minute request for a stay of execution.
Attorneys for Biros had argued the state's new, untested method would be painful and unconstitutional. The single-drug procedure was implemented to end legal challenges to the widely-used three-drug protocol, which critics claim causes severe pain.
On Monday, a lower court judge also denied an appeal, saying that Biros had not demonstrated "at this juncture" that the new protocol is unconstitutional.
But U.S. District Court Judge Gregory Frost acknwoledged that "it does not foreclose the possibility that additional evidence will indeed prove that the problems with Ohio's policies and practice rise to a constitutional error."
Ohio has been plagued with problems administering lethal injection.
Earlier this fall, the state abandoned its standard three drug protocol after nurses and a doctor were unable to execute inmate Romell Broom after 18 puncture attempts.
Broom became the first inmate in history to walk away from a planned lethal injection execution and he is now arguing that the state can't attempt to kill him a second time.
After an examination of Broom's botched execution, state officials decided to change protocol in November adopting the use of one drug -- a massive overdose of an anesthetic called sodium thiopental -- for its new injection standard.
Of the 36 states, and the federal government, that use lethal injection, most use the same method that Ohio has now abandoned: a three-drug combination of sodium pentathol, pancuronium bromide and potassium chloride. The latter two drugs serve to paralyze the inmate and then stop his heart.
In changing its protocol Ohio also established a "back up procedure" in the event that officials are unable to find an appropriate vein for the intravenous injection of the drugs. The back-up plan involved injecting the chemical directly into muscle instead of the bloodstream.
Terry J. Collins, director of the Ohio Department of Rehabilitation and Correction, authorized the direct injection of a sedative, midazolam, and an opiate, hydromoprhone, into muscle tissue to carry out the execution.
Death Penalty Opponents Say New Method Doesn't Solve Challenges
Some opponents of the death penalty applaud the fact that Ohio has agreed to stop using two of the drugs.
"This is a significant step forward," said Ty Alper, Associate Director, Death Penalty Clinic, U.C. Berkeley School of Law. "Paralyzing inmates before executing them – so we can't tell whether they are suffering – is a barbaric practice, and Ohio should be commended for stopping it."
But Alper still sees problems with the system. "Ohio still hasn't solved the problem of IV access, and given Ohio's difficulty in accessing inmates' veins that remains a serious concern. Our main concern is that if they can't establish IV access then they have to use the back up plan which is a complete unknown."
Alper says the state has to go through a more thorough vetting process of the new protocol even though it was developed in consultation with a doctor whom the state has on retainer to consult on lethal injection issues.
Richard Dieter, executive director of the Death Penalty Information Center which opposes the death penalty, agrees.
"Perhaps experts from the medical profession will agree that Ohio has chosen the best available alternative to the risky three-drug process," he said. "But such a conclusion requires an evidentiary and adversarial hearing - not a doormat of blind acceptance."
But victim's rights advocates believe the state has done enough to protect the rights of death row inmates.
Cuyahoga County, Ohio, Prosecutor Bill Mason told ABC News it doesn't matter if justice is brought with one drug or three drugs: "In all cases it is more humane than what these murderers [Kenneth Biros and Romell Broom] did to these innocent victims."
"Broom brutally raped and murdered a 14 year-old child by plunging a knife 7 times into her chest. They ought to have him in a waiting room, and as soon as this procedure is deemed successful [with Biros], they should bring him in and put him on the table before they put the equipment away," he said.
In 2008, the U.S. Supreme Court upheld the constitutionality of a three drug protocol used in Kentucky but the court left open the possibility of other methods being explored.
ABC News' Devin Dwyer contributed to this report.