Alfred Chestnut, Andrew Stewart and Ransom Watkins were sentenced to life in 1984 in the state of Maryland for the murder of a 14-year-old boy a year earlier, the BBC reported.
They were freed in Baltimore on Monday after a review of their case and overturn of their convictions by a court.
The case was reopened in 2019 after Chestnut wrote a letter to Baltimore's Conviction Integrity Unit, the report added. He tagged evidence he uncovered last year.
The trio were teenagers when they were arrested in November 1983 in connection with the murder of DeWitt Duckett, who was shot in the neck while on way to Baltimore junior high school.
"These three men were convicted, as children, because of police and prosecutorial misconduct," Baltimore state attorney Marilyn Mosby said after their release.
Her office said in a statement: "Detectives targeted the three men, all 16-year-old black boys, using coaching and coercion of other teenage witnesses to make their case."
Prosecutors said police ignored and withheld reports from multiple witnesses that identified another person as the killer. Even trial witnesses failed to identify the three in photo line-ups.
All trial witness have since recanted evidence, Mosby said.
"I don't think that today is a victory, it's a tragedy. And we need to own up to our responsibility for it," she said.
The other suspect died in 2002.
( With inputs from IANS )