A man who was in jail for nearly 50 years for a murder he did not commit has been exonerated by a judge.

Glynn Simmons, 71, was released in July after a district court found crucial evidence was not turned over to his defence lawyers.

Simmons was ruled innocent on Tuesday and Oklahoma County District Judge Amy Palumbo said: ‘This court finds by clear and convincing evidence that the offense for which Mr Simmons was convicted, sentenced and imprisoned… was not committed by Mr Simmons.’

Simmons was the longest imprisoned U.S. inmate to be exonerated, having served 48 years, one month and 18 days in jail since his conviction.

Following the ruling he said: ‘It’s a lesson in resilience and tenacity. Don’t let nobody tell you that it (exoneration) can’t happen, because it really can.’

Simmons was accused of murdering Carolyn Sue Rogers inside a Louisiana liquor store in 1974, something he has always denied.

He and his co-defendant Don Roberts were initially sentenced to death following their conviction in 1975.

Their sentences were reduced to life in 1977 and Simmons was released on parole in 2008.

glynn simmons
Glynn Simmons has spent most of his life behind bars
Simmons reacts after stepping out of the courthouse (Picture: AP)

A new trial was ordered by Palumbo in July after it was found prosecutors failed to turn over evidence like a police report that showed an eyewitness might have identified other suspects in the case.

Behenna said there is no physical evidence in the case against Simmons and confirmed she would not retry him.

She stopped short of declaring him actually innocent and a spokesperson for Behenna declined immediate comment.