New York, New York - Two US men imprisoned for decades in separate cases were exonerated on Monday after their convictions were found to be flawed and overturned by New York courts, prosecutors said.

The convictions of the men were undermined by flawed witness testimony and procedural errors, according to the applications to have the cases thrown out.

Monday's exonerations are the latest embarrassment for the New York Police Department, which has seen a string of high-profile convictions thrown out over errors and misconduct by investigators.

One of the men, Wayne Gardine, was incarcerated for more than 18 years for a murder in 1994 at the height of New York's crack cocaine epidemic. He now faces deportation to his native Jamaica despite being exonerated and having served the entirety of his original sentence.

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The other, Jabar Walker, was sentenced to two terms of 25-years-to-life for the killing of two men in a car in 1995 in the same area as the murder for which Gardine was convicted.

Walker, who was freed following his hearing, was shown in images published by local media sporting a gray-flecked goatee, beaming as he stood flanked by supporters and family.

"Walker, who was 23 at the time of his conviction, was released from prison today after serving 25 years of two consecutive terms of 25 years-to-life in prison," the New York district attorney's office said.

"The Office today joined the Legal Aid Society's motion to vacate and dismiss the indictment of Gardine based on the Office's finding of newly discovered evidence," the New York DA said.

"Gardine, who was 22 at the time of his conviction, served nearly three decades in prison before he was released on parole in 2022. He was then transferred to US Immigration and Customs Enforcement, where he remains in custody."

Gardine "is still not a free man and faces additional and unwarranted punishment if deported," said Lou Fox, Gardine's lawyer at the Wrongful Conviction Unit at The Legal Aid Society, which took on his case.