HUNTSVILLE, Texas — Attorneys for a 66-year-old Texas death row inmate say his health problems make him unsuitable for lethal injection scheduled for this week so they're proposing he be rolled in his wheelchair in front of a firing squad or be administered nitrogen gas to cut off oxygen to his brain until he stops breathing.

If the state doesn't accept one of their alternatives, lawyers for confessed multiple killer and rapist Danny Paul Bible contend his lethal injection, set for Wednesday evening, should be halted because it would be unconstitutionally cruel and present a "substantial risk" of being botched due to his "unique constellation of medical issues."

The 5th U.S. Circuit Court of Appeals refused the appeal Tuesday, affirming a decision from a federal judge in Houston last week.

Bible's attorneys said they would take the case to the U.S. Supreme Court.

No one disputes the guilt of Danny Paul Bible, who is set for execution on Wednesday evening. via Reuters

State attorneys argued the civil rights lawsuit was a "meritless tactic" to delay his "well-deserved execution." Neither firing squad nor nitrogen gas are legal execution methods in Texas and the state Legislature isn't scheduled to meet again until next year. A handful of death penalty states allow nitrogen hypoxia, although the method hasn't been used. Three Utah inmates have been executed by firing squad, the most recent in 2010. Utah now allows that method if drugs for execution are unavailable.

No one is disputing Bible's guilt for a Houston slaying nearly 40 years ago that went unsolved for two decades before a jury convicted him of it and sent him to Texas death row.

Bible, a drifter with a record of violence in several states, would be the seventh convicted killer executed this year in Texas, equaling the state's total for all of 2017. He'd be nation's the 12th prisoner executed this year.

Bible's lawyers sought a reprieve, a restraining order and an injunction to block his execution, arguing Bible had no suitable sites on his body for IVs to deliver a lethal dose of the sedative pentobarbital and that severe tremors accompanying his Parkinson's disease would complicate insertion of IV needles. They also warned of a problematic execution like ones in recent years in Ohio and Alabama.

Stephen Hoffman, an assistant Texas attorney general opposing the lawsuit, said the court "should give little consideration to isolated examples of problematic executions in other states when it has numerous uneventful Texas executions upon which to base its opinion." Texas has carried out 551 executions since 1982, tops in the nation.

Hoffman pointed out IVs successfully have been used to draw blood from Bible as part of his medical care.

Bible was tracked down in 1999 and arrested in Fort Myers, Florida, for a Louisiana rape. He asked detectives in West Baton Rouge, Louisiana, for a Bible and a pack of cigarettes and began talking, acknowledging four killings, including a 4-month-old boy, and at least nine rapes. Five rapes were northeast of Houston in San Jacinto County.

The four slayings included 20-year-old Inez Deaton, whose 1979 killing in Houston went unsolved for nearly two decades. Deaton, found on the banks of a Houston bayou, had been raped and fatally stabbed with an ice pick and was a friend of Bible's cousin. A jury that convicted him in 2003 of Deaton's slaying decided he should die.

The three other killings, all west of Fort Worth on the same day in May 1983, included Bible's sister-in-law Tracy Powers and her 4-month-old son, Justin, in Parker County, and her roommate, Pam Hudgins, in Palo Pinto County. He pleaded guilty to Hudgins' death and was sentenced to 25 year in prison, served seven and was released to Montana in 1992 on a form of parole known as mandatory supervision.

At his Houston trial for Deaton's slaying, prosecutors presented evidence of robberies, thefts, assaults and abductions, including the rape of an 11-year-old girl in Montana and his confessions to repeated sexual assaults of young nieces from 1996 to 1998.

Attorneys earlier argued unsuccessfully that Bible was left disabled and in permanent pain after a prison van taking him to death row in 2003 crashed, killing a corrections officer and the driver of another vehicle involved in the wreck.