A lawyer for a man convicted in the Black Sunday blaze that killed two firefighters wants the verdict overturned because a juror contacted a witness during the trial.

The unidentified Bronx juror sent an e-mail on Feb. 9, the day of closing arguments in the high-profile trial, inviting the witness to join a social networking Web site, defense lawyers said Tuesday.

"We'll make a motion to vacate the verdict," said David Goldstein, the lawyer for building manager Cesar Rios, who was convicted of criminally negligent homicide.

"There was no impartiality," Goldstein argued, saying the juror could not have been impartial while "asking [the witness] to join some kind of organization."

Defense lawyers confirmed they had received the documents Monday. Prosecutors also sent the papers to the judge, along with an e-mail exchange between the two that began after the Feb. 18 verdict.

The names of the juror and the witness were redacted, but it appeared the witness is one of the four firefighters who survived the devastating 2005 fire on E. 178th St.

"I just wanted you to know that we all fought our hardest for all of you and every second was worth it," the juror wrote after the trial had finished, the documents said.

The firefighter, who did not respond to the initial invitation, is not believed to have done anything wrong.

Although jurors are barred from contacting witnesses in a case until a trial is complete, it's unclear if the e-mail gives the judge a reason to declare a mistrial.

The juror could face contempt charges for ignoring orders not to contact witnesses.

Rios faces up to four years in prison. Prosecutors had no comment.