A co-defendant in a negligent homicide case stemming from a 2008 tower crane collapse that killed two New York City construction workers quietly changed his plea to guilty earlier this month and has promised to help prosecutors convict his former boss, James F. Lomma, who had owned the crane, court transcripts show. The trial had been set to start next month.

Manhattan Criminal Court Judge Thomas Farber granted a request by defendant Tibor Varganyi, 65, former head mechanic at Lomma’s firm, New York Crane, to change his plea in a closed courtroom, but the judge refused to seal the records of his allocution hearing.

“Obviously, as I mentioned, I will do nothing to advertise this to anybody,” Farber said. “I am also not doing anything to hide it.”

Lomma, also 65, whose own criminal trial had also been set for November, ran the crane rental firm and a related firm, J.F. Lomma. Inc. Prosecutors indicted Lomma, Varganyi and the firms in 2010 in the deaths of union crane operator Donald C. Leo and another worker, Ramadan Kurtaj. They allege that the defendants failed to correct a rotator gear on the crane that snapped, causing it to collapse and rain steel debris onto an Upper East Side neighborhood. The defendants had maintained their innocence and pleaded not guilty.

They face charges of second-degree manslaughter, second-degree assault, criminally negligent homicide and second-degree reckless endangerment, with a 15-year jail sentence possible on the first charge. Defendants pleaded not guilty to all the charges.

Varganyi signed a cooperation agreement to testify against Lomma and the firms in exchange for a probable non-jail sentence, transcripts indicate.

“I said if it is the People's position that based on all the factors they need to consider that this is an appropriate sentence, yes, I would impose a non-jail sentence if that was the agreement of both parties following the completion of this agreement,” Judge Farber said.

Judge Farber also told Varganyi that his guilty plea might complicate his citizenship status, although the defendant said he has lived in the U.S. for more than 30 years. Varganyi told the judge that he was aware of the risks of his reversal and that he was not coerced into changing course.

Varganyi’s lawyer Matthew Brief declined to elaborate on the transcripts in a phone interview.

Lomma’s lawyer Paul Shechtman did not immediately reply to a request for comment.