Missouri is planning to execute a man who's missing nearly 8% of his brain

Missouri is planning to execute a convicted cop-killer named Cecil Clayton who lost almost 8% of his brain in an accident.

His death at the hands of the government could violate the Constitution's ban on cruel and unusual punishment.

In 1972, Clayton, then 32, was sawing wood when a piece flew off the log and pierced his head. To save his life, doctors removed 20% of his frontal lobe, totalling 7.7% of his brain, according to a petition filed by his lawyers.

"There was a profound change in him that he doesn't understand, and neither did his family," Elizabeth Unger Carlyle, one of Clayton's lawyers, told The New York Times.

The frontal lobe is tied to impulse control and problem-solving, as The Times reported.

As a result of the accident, Clayton suffers from dementia, depression, and general psychosis, including hallucinations, according to his lawyers. People, even Clayton's own family, made him so nervous, he couldn't stand to be around anyone, his doctor wrote in 1979. Confused and anxious about his state of mind, he often yelled or became violent. Other medical records also document Clayton's pattern of concerning behavior.

In 1996, deputy sheriff Christopher Castetter responded to a domestic disturbance involving Clayton and his ex-girlfriend. Castetter was later found sitting in his patrol car with a bullet in his head. Clayton was arrested, found guilty, and sentenced to die for the murder.

Since then, however, the Missouri Supreme court has heard experts testify on five occasions that Clayton isn't competent enough to face execution. Even a psychiatrist, appointed by the Missouri Department of Corrections to assess his mental state, determined the same.

Regardless, the Missouri Supreme Court has ruled the state should proceed with the execution, set for Tuesday, March 17. Four of three justices found that since Clayton can understand why he's facing the death penalty, he's fit for his punishment.

In multiple cases, the US Supreme Court has ruled that executing an insane or mentally ill person violates the Eight Amendment's ban on cruel and unusual punishment. The high court, however, has never truly specified a definition of mental illness, which leaves the interpretation up to individual states.

Clayton's lawyers have now asked the US Supreme Court to halt the execution.