-- It turns out the Oddfather isn't.

Vincent "the Chin" Gigante dropped his three decade-long ruse today and acknowledged that he had tricked doctors into believing he was a low IQ, mental incompetent who paraded around Greenwich Village in his pajamas and a bathrobe.

He was, in fact, the reigning boss of the Genovese crime family, the most powerful of this city's five mob concerns. Today he pleaded guilty to obstruction of justice in U.S. District Court.

Judge Leo Glasser read the charge to Gigante in a slow, loud voice. You agree, Glasser asked the mobster, that you "knowingly, intentionally misled doctors" who were evaluating your competency to stand trial?

Gigante gave a weary nod and answered in a whisper, "Yes, your honor."

Gigante, 75, already is living rent-free in a federal penitentiary, serving 12 years for a 1997 conviction on racketeering and murder conspiracy. This latest charge will add three years to his sentence.

His son, Andrew Gigante, 46, also pleaded guilty today to conspiracy to commit extortion and will be sentenced to two years in prison.

Like a good method actor, Vincent Gigante -- also known as the Oddfather -- was slow to surrender his role today. He ambled into the federal courtroom just before 10 a.m., a disheveled, gaunt-cheeked man, his eyes glazed, his speech halting. He wore two white T-shirts, wrinkled khaki pants and a blue prison smock. He lowered himself into a chair and slowly let his head droop to the side.

Across the room, a prosecutor rolled his eyes.

Prosecutors said Gigante could be heard on audiotapes in prison, chatting quite lucidly with visitors and showing a "coherent, careful and intelligent" interest in the business affairs of the Genovese family.

"Vince Gigante was a cunning faker," Roslynn R. Mauskopf, the U.S. attorney, said after the sentencing. "Those of us in law enforcement always knew it was an act."

Gigante ruled for two decades as CEO of the Genovese family, but he was best known for making an art form of dementia. If a cop or prosecutor was near, he would slobber, waggle his head and talk to himself.

Once a FBI agent burst into his mother's apartment in Lower Manhattan only to find the crime boss standing naked in the shower, with his umbrella up.

Gigante took up the mental illness dodge in the late 1960s, after serving time on various drug and bribery charges. Between 1969 and 1999, he checked himself into a suburban hospital for treatment 22 times.

It worked. As the FBI snagged one mob boss after another, Gigante remained free. He never used the telephone at his Triangle Social Club on Sullivan Street -- he preferred to whisper in ears or stop at public phone booths in his pajamas. Fellow gangsters never spoke his name. Most signified him simply by touching their chin -- a move that inspired his nickname.

On the occasions when he did stand trial, Gigante's relatives hired teams of psychiatrists, who would dutifully report that Gigante suffered from paranoid schizophrenia, dementia and Alzheimer's disease. The Rev. Louis Gigante, a Catholic priest and former city councilman, took the role of his brother's custodian, declaring that the reputed mob boss had an IQ of 70.

"My brother was a street kid, but to label him as a boss of a conglomerate that extorts is ridiculous," Louis Gigante told the media. "He didn't run anything because he couldn't run anything."

In fact, Gigante has spent more than a half-century in the mob, recruited as a mobster in training by Charles "Lucky" Luciano. Gigante was an able apprentice, although he did bungle an ordered hit on Frank Costello, the former chief of the Genovese family.

Costello took the hint and retired soon after.

The Genovese crime family's interests are broad. At its height, the family writ extended from Little Italy to the New Jersey docks to the warehouses of Miami, with interests ranging from loan-sharking to restaurants, seafood distribution and vending machines. Able modernizers, the family branched into narcotics and pornography after World War II.

Once the Genovese family had 700 members, known as soldiers. Relentless prosecutions and an unhealthy lifestyle have reduced that number to about 200 today.

Gigante was a feared boss. Asked to settle a Philadelphia mob war, prosecutors charged that he ordered up a batch of murders. He also tried to arrange a premature death for John Gotti, chief of the rival Gambino crime family.

His fellow mobsters respected Gigante's willingness to play the crazy man -- up to a point. "He's got to worry," "Fat" Tony Salerno was heard saying on a prosecution recording. "If he gets pinched, all them years he spent in that [expletive] asylum are for nothing."

In that light, today's plea agreement was not about jailing Gigante. He is already in prison until 2007 and leadership of the Genovese family has passed on. The point today was to prove he was sane.

After the sentencing, Andrew Gigante asked if he might spend a few minutes visiting with his ailing father. Judge Glasser agreed and Andrew, wearing a black jacket, black shirt and black tie with polka dots, walked over and sat with his father.

The weak dispirited man of a few minutes earlier disappeared. The elderly mobster fixed his eyes intently on his son and lawyer. Holding his heart medication in his hand, Gigante told soft jokes and seemed to be advising his son. It was as though, after a few minutes, he was back in the Triangle Social Club.

Even the prosecutors kept a respectable distance. After 10 minutes, Gigante nodded, rose easily, and smiled and waved at the judge.

"Thank you," Gigante said.

Andrew Gigante, son of mob boss Vincent "the Chin" Gigante, leaves U.S District Court in New York yesterday after pleading guilty to conspiracy to commit extortion.