In 1997, Firefighter John Driscoll was seriously hurt in an apartment building on E. 63rd St. As black smoke choked the stairwell, a hose jerked in his hands. He tumbled headfirst down the staircase.

For weeks, herniated discs in his neck kept him in a hospital. He endured five surgeries and was forced to retire from the FDNY.

Driscoll, 48, sued the building's managers, Tower Associates, alleging there were no smoke detectors and that managers delayed 15 minutes before calling 911.

The case went before Manhattan Supreme Court Justice Marylin Diamond.

No one told Driscoll that Tower's law firm also personally represented Diamond in another courtroom. Diamond, who dismissed Driscoll's personal injury lawsuit, never disclosed it.

"I don't think anybody was aware of it," Driscoll said. "It's a conflict of interest, and if my lawyers can find a way to reverse it, I'm sure they will."

Judges cannot rule on cases in which their own lawyers represent one side.

A June 1999 ethics opinion states: "A judge must exercise recusal where an attorney who represented the judge and members of the judge's family appears before the judge within two years of the representation."

Under New York law, a building owner is liable for firefighter injuries if they arise from a violation of city rules.

Driscoll's lawyers, the firm of Barasch, McGarry, Salzman, & Pension, made that argument to Diamond. The firm of Gould & Cimino, representing Tower, claimed smoke had nothing to do with Driscoll's injuries.

Gould & Cimino also represented 920 Park Ave., a luxury high-rise owned by Diamond and her family. The building was sued in 1999 and settled in April 2002.

In March 2002, Diamond dismissed Driscoll's case. Driscoll asked her to reconsider. She refused.

"My whole life changed," Driscoll said. "I don't sleep through the night. I can't lift weight. I'm not as athletic as I used to be. I can't hold a job, because employers need you to sit or stand for a prolonged period of time."

His lawyer, James McGarry, has appealed.

"We're going to put this conflict-of-interest issue out there," he said.

In fact, as Gould & Cimino represented Diamond's Park Avenue building, the firm appeared before Diamond in six other cases as well, records show.

In August 2003, Diamond suddenly recused herself from one of those cases. Lawyers say she never gave a reason. Diamond refused repeated requests for comment.