COLUMBUS, Ohio (AP) — At about 450 pounds, Ohio death row inmate Ronald Post is so fat that his executioners won’t be able to find veins in his arms or legs for the lethal injection, and he might even break the death chamber gurney, his lawyers say.

If the state is forced to use a backup method that involves injecting the drugs directly into muscle, the process could require multiple doses over several hours or even days and result in a grueling and painful end, they say.

Post, who gained close to 200 pounds on death row, is trying to stave off execution Jan. 16 for the 1983 killing of a motel clerk during a robbery, arguing that because of his obesity, an attempt to put him to death would amount to cruel and unusual punishment.

State officials say Post, 53, can be humanely executed under both Ohio’s usual method and the untested backup procedure. The warden at the prison where the death chamber is situated even tested the gurney by piling 540 pounds of weights on it for two hours.

Post has not presented “sufficient evidence demonstrating that his obesity or other physical conditions will present a substantial risk that his execution cannot be conducted in a humane and dignified manner,” Assistant Attorney General Charles Wille said in court papers.

A federal judge in Columbus will hold a hearing on Post’s claim later this month.

Post’s case is not without precedent: In 1994, a federal judge in Washington state ruled that convicted killer Mitchell Rupe, at more than 400 pounds, was too heavy to be hanged because he might be decapitated. After numerous court rulings and a third trial, Rupe was sentenced to life in prison, where he died in 2006.

If Post manages to stop his execution because of his weight, the legal precedent may not be far-reaching, because of the very small number of death row inmates who are that obese, said Deborah Denno, a Fordham University law professor and expert on lethal injection. And she said it is unlikely prisoners would begin stuffing themselves to try to fend off execution.

Richard Dieter, executive director of the Washington-based Death Penalty Information Center, which opposes capital punishment, predicted states will find a way around obesity claims by adjusting their execution procedures, perhaps by changing the drug or the dosage.

“Inmates probably will recognize that that’s a thin straw to hang your hopes on,” he said.

In 2007, it took Ohio executioners about two hours to insert IVs into the veins of condemned killer Christopher Newton, who weighed about 265 pounds.

At 6-foot-2½, Post weighed 260 pounds around the time he was moved to death row in 1985. His weight has gone up and down behind bars, and at one time he lost 150 pounds through dieting, his lawyers say.

But knee and back problems have made it difficult to exercise, his lawyers say. They also say Post’s request for gastric bypass surgery was denied, he has been told not to walk because he might fall, and severe depression has contributed to his inability to control how much he eats.

The Ohio prison system would not comment on how Post gained so much weight behind bars. They said meals are served in reasonable portions and seconds are not allowed, and they provided copies of prison menus that list healthier options such as low-fat milk, vegetarian patties and mixed vegetables.

Inmates can buy sweet and salty snacks from the commissary.

A doctor who examined Post for the defense said Post does not have accessible veins in his arms, hands or legs.

“Given his unique physical and medical condition there is a substantial risk that any attempt to execute him will result in serious physical and psychological pain to him, as well as an execution involving a torturous and lingering death,” Post’s attorneys argue in court papers.

His lawyers have indicated they would fight any attempt by the state to employ a third possible procedure: the “cut-down” method, in which executioners cut into the condemned man’s arms to find a vein. Ohio’s execution policies don’t call for such an approach, and it is unclear if the state can go ahead with such a procedure without court approval.