This puts a little damper on the Robert Morgenthau retirement celebrations: old-timers may remember that in 1990 a bouncer was shot dead at the Palladium (now an NYU dorm) on 14th Street. David Lemus and Olmedo Hidalgo went away for the murder, though they claimed they weren’t at the club. A few years later, during an investigation, assistant DA Steven Cohen came across a gang-banger who said he did the crime, not Lemus or Hidalgo, but couldn’t get the verdict overturned with this evidence and, after leaving the DA’s office, worked with the wronged men to establish their innocence. When the case finally came to trial again, the DA’s office still vigorously defended the convictions — though one of the prosecutors, Daniel Bibb, later admitted he was less than vigorous about it. Lemus and Hidalgo were eventually cleared, and today Hidalgo got $2.6 million from the city and state in his civil rights suit against them. Lemus has a suit going at present.