In the event that method fails, a backup plan allows executioners to inject drugs directly into muscles.
Ohio overhauled its procedure after the failed attempt to execute Romell Broom, a procedure halted by Gov. Ted Strickland in September. Executioners tried for two hours to find a usable vein for injection, hitting bone and muscle in as many as 18 needle sticks that Broom said were very painful.
Broom, 53, has appealed the state's attempt to try again. The state had two goals in changing its process. Switching to one drug was meant to end a 5-year-old lawsuit that claims Ohio's three-drug system was capable of causing severe pain. Injection experts and defense attorneys agree the single dose of thiopental sodium will not cause pain.
The backup procedure allowing muscle injection was created in case a situation like Broom's execution happens again.
States are watching Ohio's change, but none have made a similar switch. Florida, Kentucky, South Carolina, Texas and Virginia are among those saying they will keep the three-drug method.
Biros reached the holding area for death row inmates at the Southern Ohio Correctional Facility in Lucasville shortly before 10 a.m. Monday. The small cell is about 15 feet from the chamber where inmates are put to death.
It's the second trip to Lucasville for Biros, who spent more than 30 hours in the holding cell in March 2007 before the U.S. Supreme Court stopped his execution and allowed him to challenge Ohio's method at the time, involving three drugs. Biros was resting and appeared relaxed, prisons spokeswoman Julie Walburn said.
Injection experts agree the execution will take longer with the single dose of thiopental sodium than the previous three-drug system. Ohio inmates have generally taken about seven minutes to die. Mark Dershwitz, an anesthesiologist who consulted with Ohio, estimates death could now come in 15 minutes.
Witnesses will be allowed to stay and watch for as long as it takes, Walburn said Monday.
A federal judge earlier Monday refused to delay the execution, and Biros immediately appealed to the 6th U.S. Circuit Court of Appeals in Cincinnati. The appeals court rejected his request for a stay Monday night.
Biros argued that the state has failed to fix the problems that led to the unsuccessful execution attempt in September. He said the state still relies on unqualified executioners and lacks limits on how long they are allowed to try to find a vein.
District Judge Gregory Frost in Columbus said in his ruling that it appears unlikely that Biros can "demonstrate that those risks rise to the level of violating the United States Constitution."
The state addressed the judge's notation about constitutionality in its response Monday to Biros' appeal and also said he could not show that Ohio's method presented a substantial risk that he would suffer severe pain.
Frost said Ohio's execution system still has flaws that "raise profound concerns and present unnecessary risks." He also said he is concerned about the competency of Ohio's executioners and how much they appear able to deviate from the state's written execution rules.
In asking Frost for a stay, Biros had argued that the new execution method still left vein access issues unresolved, subjecting him to the risk of severe pain, and had described the new one-drug approach as "impermissible human experimentation."
The judge, in his ruling, called the arguments "unpersuasive."
All 36 death penalty states use lethal injection, and 35 rely on the three-drug method. Nebraska, which recently adopted injection over electrocution, has proposed the three-drug method but hasn't finalized the process.
The 6th Circuit on Friday rejected a separate but related request to delay Biros' execution, a decision he appealed Monday to the U.S. Supreme Court.
Biros killed 22-year-old Tami Engstrom near Warren in 1991 after offering to drive her home from a bar, then scattered her body parts in Ohio and Pennsylvania.
