A 71-year-old man who spent nearly five decades in prison for a murder he did not commit is to receive a $7.15 million settlement from the US city that convicted him.

Glynn Simmons, who is Black, served more time behind bars before being exonerated than any other inmate in US history, according to The National Registry of Exonerations.

Simmons was released last year after serving a total of 48 years, one month and 18 days in prison.

On Monday, councillors in Edmond, Oklahoma, voted to proceed with a settlement for Simmons to resolve claims against the city and one of the detectives who helped put him away, public records showed.

Lawyers for Simmons said the payment represented a "partial settlement" of his lawsuit "against the cities and police who falsified evidence... to frame him for murder."

"Mr. Simmons spent a tragic amount of time incarcerated for a crime he did not commit," said lead attorney Elizabeth Wang.

"Although he will never get that time back, this settlement with Edmond will allow him to move forward while also continuing to press his claims against" Oklahoma City and a leading detective.

A spokesperson for Edmond declined to comment when approached by AFP.

Simmons and another man, Don Roberts, were sentenced to death in 1975 for the murder the previous year of a 30-year-old liquor store clerk during a robbery in Edmond.

Their sentences were later commuted to life in prison.

Simmons and Roberts were convicted solely on the basis of the testimony of a teenage customer who was shot in the head during the robbery, but survived.

She picked them out of a police lineup but a subsequent investigation cast significant doubt on the reliability of her identifications.

Both men had said at trial that they were not even in Oklahoma at the time of the murder.

US District Court Judge Amy Palumbo threw out Simmons's conviction in July last year. He was officially declared innocent in December.

Roberts, Simmons's co-defendant, was released from prison in 2008, according to The National Registry of Exonerations, a project run by three US universities.