For the past 4,380 days, David Lemus and Olmeda Hidalgo have sat in separate cells in a maximum-security prison upstate for a murder they say they did not commit, and for the past 4,380 days, virtually nobody was listening.

Now, searching for a breakout strategy in her bid to unseat a legendary Manhattan district attorney, Robert Morgenthau, his challenger, Leslie Crocker Snyder, called on Mr. Morgenthau to order a new trial in the murder 15 years ago of a bouncer at the Palladium nightclub and to arrest an alleged Bronx gang member and career felon believed to have taken part in the killing.

At a press conference on the steps of City Hall yesterday, Ms. Snyder, a former sex-crimes prosecutor and state Supreme Court judge, said prosecutors in Mr. Morgenthau’s office “mishandled the case” against Lemus and Hidalgo by failing to disclose vital information to defense attorneys representing the two men.

That information consisted of tips to police that a Bronx gang member, Thomas “Spanky” Morales, who served more than 10 years in state and federal prisons for gang and racketeering charges, had allegedly taken part in the shooting, along with another gang member, Joseph Pillott, who is now serving a sentence of 15 years to life in federal prison on similar charges.

In recent statements to the judge presiding over the continuing appeal by Lemus and Hidalgo for a new trial, the prosecutor handling the case for the Manhattan district attorney, Daniel Bibb, has said he, too, has come to believe Morales played a role in the murder, and the question of whether to arrest and prosecute the man for the crime has been “the subject of continuing discussions in my office.”

Flanked by Lemus’s and Hidalgo’s current pro-bono defense attorney, Steven Cohen, and the retired New York detective that probed the initial murder investigation, Robert Addolorato, Ms. Snyder said the failure to arrest Morales was “an act of injustice.” The victims, she said, were not only Lemus and Hidalgo, who are currently serving prison sentences of 25 years to life, but all New Yorkers, faced with the prospect of an alleged murderer “walking our streets.” Morales, released from prison in 2002, could not be immediately reached yesterday.

In a statement, a spokeswoman for the district attorney’s office, Barbara Thompson, said prosecutors “had conducted a complete re-investigation of the Palladium shooting in light of new allegations.” The new investigation included interviews with more than 50 witnesses across 14 states, she said, and the evidence uncovered has ultimately led to Lemus’s and Hidalgo’s current attempt in state court to request a new trial.

Mr. Morgenthau’s office has contended that even if there was, indeed, at least one other participant in the bouncer’s killing, Lemus and Hidalgo were involved in it. The defense lawyers have argued the two men who were convicted had no involvement in the crime.

In statements yesterday, Mr. Addolorato, now a security supervisor at the Museum of Modern Art, said that as a first-grade detective based in the Bronx, he received tips from an informant, along with testimony obtained from Pillott and relatives of Morales, claiming that Morales had fired the shots that ultimately killed the nightclub bouncer, Marcus Peterson, 23, a bodybuilder from Brooklyn. When he tried to tell the assistant district attorney handling the case, Stephen Sarracco, that Morales had been fingered as a potential suspect, Mr. Addolorato said, Mr. Saracco found the new evidence wasn’t “on the money.” Mr. Saracco, who no longer works for the district attorney, could not be reached last night.

The next court date for Lemus and Hidalgo is scheduled for April 18.

If she is elected in November, Ms. Crocker also said yesterday, she would create and implement a Second Look Bureau, an internal office that would act as a watchdog agency designed to ferret out cases where defendants were falsely convicted.

So far, she has raised $889,503 for the race and has the endorsement of 10 police unions – many of whose members do not reside in New York and cannot vote for her.