Vincent "Chin" Gigante, the mob boss known as the "Oddfather" for his aimless rambles around Greenwich Village in a bathrobe while appearing to be mentally ill, was convicted today of racketeering and two counts of conspiracy to commit murder.

Gigante, who looked up but showed no emotion when the verdict was read, was ordered to turn himself in within 24 hours at a federal prison hospital in North Carolina where he will be held for 30 days of examination and treatment.

The convictions, for which Gigante could serve 30 years, amount to a virtual life sentence for the 69-year-old defendant, whose lawyers claim he is too incoherent to participate in his defense. He has appeared in court during the past month in a wheelchair while intermittently muttering to himself.

Federal prosecutors have long described Gigante as the cunning boss of the Genovese New York crime family. The government has also insisted -- and a federal jury of eight women and four men apparently agreed today -- that for years Gigante has been acting when he appeared publicly to be out of his mind.

Witnesses in the month-long trial testified that Gigante gave strict orders, punishable by death, to his underlings that they were not to mention his name or nickname in discussions of mob business. Apparently aware that federal tape recordings have led to convictions of top Mafia leaders, witnesses said, mobsters referred to Gigante only as "that guy," while touching their chins.

"He has embarked on a determined crusade to elude prosecution by putting on a charade of mental incompetence," U.S. Attorney Zachary W. Carter said after the verdict. "The attorneys of this office . . . were willing to match his efforts with herculean efforts of their own {so} that his charade was finally brought to an end."

Gigante's doctor said after the verdict that his patient was "unaware of what's going on." Bernard Weschler said Gigante had an attack of high blood pressure before the verdict and was given Thorazine and Valium. "People are crying all around him, and he doesn't know what's happening now," Weschler said.

As part of one of the most costly and time-consuming mob investigations this decade, the federal government invested more than seven years trying to put Gigante in prison. Carter said that Gigante's conviction will have "a devastating impact on the operations of the Genovese family and organized crime generally."

Andrew Weissmann, an assistant U.S. attorney and chief courtroom prosecutor in the case, described Gigante as "the last of the long-term organized crime bosses in New York City. Anyone else that takes over now will not have that history or power hold on the rest of the city."

The government did not win on the seven murder charges that were at the heart of much of the testimony by 12 FBI agents and six turncoat mobsters. The witnesses apparently failed to convince the jury that Gigante had ordered the killings, six of them related to a Philadelphia gang war in the early 1980s.

Most of the mobsters' testimony -- while rich with Mafia lore and spiced with details about Gigante supposedly ordering gangsters to be "whacked" -- was based on second- and third-hand information. Only Peter Savino, a onetime Genovese associate, directly tied Gigante to a crime, saying that "Chin" had ordered the murder of a teenage hoodlum in 1983, but then he changed his mind.

U.S. District Judge Jack Weinstein scolded the prosecution for presenting a "stale" case. Gigante's lawyers were so confident that the government had failed to make a convincing case that they astonished courtroom observers by resting their case this week without calling a single witness for the defense.

Defense attorney Michael Marinaccio promised an appeal and described the jury's verdict as a "gross injustice" based on "a mountain of hearsay."

"We think that there was a great deal of prejudice that we had to overcome," Marinaccio said. "Perhaps the jury wasn't able to put aside what they believed coming to the cse about organized crime in general and Mr. Gigante in particular."

Besides claiming Gigante's mental incompetence, defense lawyers said they will appeal the judge's decision to allow Savino to testify on closed-circuit television.

The jury convicted Gigante of conspiring to murder Savino, as well as plotting to kill New York crime boss John Gotti. Neither slaying occurred; Gotti is serving a life sentence for murder and racketeering. The star witness in the government's case was Salvatore "Sammy the Bull" Gravano, confessed murderer of 19 and a former number two man in the Gambino crime family. But Gravano failed to directly link Gigante to a single murder. His credibility was damaged when defense lawyers pointed out discrepancies between his testimony and a best-selling book, "Underboss," from which Gravano has made more than $250,000. Special correspondent Devon Spurgeon contributed to this report. CAPTION: Vincent Esposito helps his father, Vincent "Chin" Gigante, on the way to Gigante's trial in New York. Gigante is to be held at a federal prison hospital in North Carolina for initial examination.