An inmate serving life for murder in the US state of Iowa offered a novel legal appeal, saying he should be released because he "died" four years ago.

However the Iowa Court of Appeals was unmoved by Benjamin Schreiber's bid for freedom ruling that the argument - however original - was "unpersuasive."

Schreiber, who was handed a whole life term without the possibility of parole after bludgeoning a man to death in the 1990s, became gravely ill in March 2015 when large kidney stones led to septic poisoning.

After he was rushed unconscious to a hospital, doctors had to revive the "dead" man five times. They then operated to repair damage done by the kidney stones. 

Schreiber, 66, was eventually returned to prison.

In a court filing in April 2018, Schreiber claimed that because he had momentarily died, his life sentence had technically been completed. 

His lawyer argued that Schreiber had been sentenced to life without parole "but not to life plus one day."

The district court was not buying it, however, calling that argument "unpersuasive and without merit."

Schreiber's lawyer then took the case to the appeals court, which ruled Wednesday that the convict couldn't have it both ways.

"Schreiber is either alive, in which case he must remain in prison, or he is dead, in which case this appeal is moot," the court said in a six-page ruling. 

The possibility that he is "dead," the court added in a footnote, seemed "unlikely" given that the appellant had himself signed legal documents in the case.

Adding a nail to Schreiber's legal coffin, the court said the sentence he is serving in the Iowa State Penitentiary will not end until a medical examiner declares him dead.

Schreiber has been in prison since 1996. He was convicted in the bludgeoning death that year of a 39-year-old man in a plot carried out with the man's girlfriend.