A man who spent 24 years in prison before being retried and acquitted in a 1989 New York City murder is suing police, saying detectives mishandled the investigation.

Derrick Deacon, 58, is seeking unspecified damages in a lawsuit filed on Wednesday against the city. The city Law Department had no immediate comment.

Mr Deacon was convicted in the 1989 shooting death of a teenager during a robbery in a Flatbush, Brooklyn, apartment complex.

Derrick Deacon, 58, hugs his lawyer on being freed after almost 25 years for a murder he didn't commit in November 2013. He is now suing the city of New York for unspecified damages

He was granted a new trial in 2012 after one witness recanted her original testimony, saying police or district attorney investigators had threatened her.

Colleen Campbell had told investigators Deacon was not the man she saw fleeing in a stairwell after the shooting, but she was coached to give vague testimony at trial, with authorities threatening to take her children if she didn't cooperate, according to The New York Post last year.

An FBI cooperator also identified a different man as the shooter.

The convicted man was granted a retrial after a Jamaican gang member came forward saying members of a rival gang had killed the victim, 16-year-old Anthony Wynn, in Prospect Lefferts Garden building.

It took a jury nine minutes to acquit Deacon in 2013.

Mr Deacon's lawyer, Earl Ward, says the case reflects 'gross misconduct' by detectives.

He also has an ongoing $25 million lawsuit against the state.

The 58-year-old has had therapy to help acclimatize to the 'new world' and deal with the loss of family members, including his mother, who passed away while he was in prison.