CHICAGO (CBS) — Justice will never come for a 53-year-old inmate who was fighting for a new trial.

His life ended Wednesday behind bars.

Anthony McKinney was 18 when he confessed to shooting and killing a security guard in 1978. McKinney would later claim that he confessed only to stop Harvey Police from beating him with pipes.

In 2008, the Northwestern University School of Law’s Center on Wrongful Convictions got involved. Executive Director Rob Warden said they petitioned for a new trial.

“We came up with what we think is really overwhelming evidence that he was innocent and yet there was almost a five-year period that we never got a hearing,” said Warden.

McKinney was found alone and unresponsive in his locked cell.

Foul play is not suspected and no official cause of death has been determined.

His lead attorney said McKinney might have been exonerated if not for delays in the legal process.