John Gotti put the fix on the federal racketeering jury that acquitted him five years ago and catapulted him to fame as a "Teflon Don," his former underboss has told prosecutors.

Salvatore (Sammy Bull) Gravano, who became an informer two months ago, has also told prosecutors that another jury that acquitted three Gotti associates of heroin charges two years ago also was compromised by Gotti, law-enforcement sources told the Daily News.

Meanwhile, on a day of many developments in Gotti's pending murder and racketeering trial, prosecutors revealed they were investigating jury tampering in the 1987 case even before the jury returned its stunning acquittal.

Prosecutor John Gleeson disclosed that the FBI had obtained the identities of the supposedly anonymous jurors, which drew charges of government tampering by Gotti's brother Peter and defense lawyers.

Prosecutors unaware
"That's the stuff they always accuse the Gottis of doing," said Peter Gotti, a spectator to pre-trial proceedings that produced some of yesterday's revelations.

In court, however, Gleeson said prosecutors trying the case were kept unaware of the investigation by a "Chinese wall" of silence.

Sources said the FBI investigation into jury tampering at the first trial was stalled until Gravano came aboard two months ago.

Until he struck a plea bargain deal, Gravano was a co-defendant with Gotti in the pending case. The indictment accused him, like Gotti, of involvement in several murders, including that of former Gambino crime family boss Paul Castellano.

Knew juror
Sources declined to provide details about the fix, saying only that it occurred after Gotti associates learned the identity of at least one juror.

Gleeson told Judge I. Leo Glasser the Gambino crime family "knew someone who knew someone on the jury. They came to the defendants. That's what happened in both cases."

The jury-tampering controversy erupted after Gleeson said he wanted to disqualify a lawyer involved in the first trial who appeared yesterday as new counsel for Gotti's co-defendant, Frank LoCascio.

Gleeson declined to say why in court but said lawyer George Santangelo, who clashed repeatedly with Gleeson and co-prosecutor Diane Giacalone in the first case, should be barred.

At one point in the first trial, after Giacalone accused him of lying and wagged her finger at him, Santangelo shouted, "Get your finger out of my face and stick it up your ass."

Santangelo appeared as a replacement for John Mitchell, a partner in a law firm that once represented Castellano.

After Gleeson privately stated his objections, Santangelo said he would fight to stay in the case. He declined to reveal Gleeson's objections.