Derrick Hamilton was convicted of murder in 1991 but judge in New York ruled key witnesses liedA 1991 murder conviction was vacated on Friday after prosecutors told a New York City judge that the state’s key witness had lied about who did it, a case linked to a retired detective at the center of dozens of wrongful conviction claims.The decision at a hearing in Brooklyn cleared Derrick Hamilton, who had served 21 years in prison before being paroled in 2011.