Three US men who spent 36 years in prison have been released after authorities say they were falsely convicted of a 1983 murder.

Baltimore men Alfred Chestnut, Ransom Watkins and Andrew Stewart were granted a writ of innocence after being convicted of the first-degree murder of a middle school student, DeWitt Duckett.

The men, who were teenagers at the time of their arrest, are now in their early fifties and are preparing to enter adulthood on the outside for the first time.