The baggy-eyed, balding man in the pin-striped suit and gold-rimmed spectacles leaned toward the jurors, looked deep into their eyes and began: "My name is Carmine Persico and I'm not a lawyer." But, shuffling his papers and confessing to being "a little nervous," he made his point: "Don't let them blind you with all the labels."

Persico, 53, is one of five alleged mob chieftains indicted 18 months ago in the federal government's boldest effort to use new racketeering laws to prove the Mafia's existence and explore its inner workings. The spectacle of a reputed underworld boss defending himself highlighted today's opening of what could be a historic trial in the decades-old battle against organized crime.

Following the indictments, one of the alleged bosses, Paul Castellano of the Gambino family, was gunned down in front of a New York restaurant. Another, Philip Rastelli of the Bonanno family, will be tried separately because he is on trial in an unrelated case in Brooklyn.

But the trial here in Manhattan is expected to provide dramatic evidence, based on hundreds of hours of secret tape recordings, that a group of Mafia families, operating since 1931, has controlled a vast web of criminal activity in New York and has extended its influence to other cities.

The remaining defendants -- three alleged bosses and five associates -- are members of "The Commission," the ruling council of the Cosa Nostra or Mafia, assistant U.S. attorney Michael Chertoff charged in his opening statement.

Their crimes, he said, included loan-sharking, labor corruption, extortion and murder. "La Cosa Nostra and Commission are not words that are coined or made up by the government. These are words these defendents use themselves, and you are going to hear them use those words on the tapes with your very own ears," he said.

He said the bosses of the five families -- Gambino, Luccese, Genovese, Bonanno and Colombo -- met often to mediate disputes, discuss the credentials of new family members, authorize murders and divide the spoils of a shakedown racket in the multimillion-dollar concrete industry in New York City, which they controlled through several labor unions.

"It's kind of like a board of directors of a big criminal company," Chertoff said.

Although lawyers for the defendants had been expected to deny the Mafia's existence, as Mafia attorneys have done in other trials over the years, the lead defense attorney, Samuel Dawson, stunned the courtroom by doing just the opposite.

"This case is not about whether an organization is in existence known as the Mafia or La Cosa Nostra," said Dawson, who represents Salvatore Santoro, alleged Luccese underboss. "There is -- right here in New York City."

He asked the jury, "Can you accept that just because a person is a member of the Mafia that doesn't mean he committed the crimes charged in this case?"

The defendants were not extorting money from concrete companies, he said, but merely setting prices to avoid competition. "This is a bid-rigging case -- an antitrust case," he said. "The government has reached for more than what the evidence shows."

Frank Lopez, attorney for Gennaro Langella, alleged acting boss of the Colombo family while Persico was in prison, boasted that the defense strategy "took the sting out of the government's case."

Although the government long has known of the Mafia's existence -- it was reconfirmed in 1957 when Federal Bureau of Investigation agents found bosses from around the country meeting in Apalachin, N.Y. -- the issue became highly politicized in the late 1960s and early '70s with Italian-American organizations protesting use of the name.

In the last five years, with new legal tools, increased use of informants, electronic surveillance and mob infiltration by law enforcement agents, the evidence has convinced most doubters.

In New York, an Italian American, U.S. Attorney Rudolph W. Giuliani, has led a vigorous assault on the five families. More than 100 alleged mobsters have been indicted in the last two years; 28 were convicted, 11 acquitted and the rest await trial.

In federal court in Brooklyn, John Gotti, alleged new boss of the Gambino family, the nation's largest, is on trial with six others on charges of racketeering, loan-sharking and murder.

In the Commission case, all the defendents have pleaded not guilty. Besides Persico, Langella and Santoro, they are: Anthony (Fat Tony) Salerno, 73, alleged boss of the Genovese family; Ralph Scopo, former president of the District Council of Cement and Concrete Workers; Anthony (Tony Ducks) Corallo, alleged boss of the Luccese family; Christopher (Christie Tick) Furnari, alleged counselor to the Luccese group; and Anthony (Bruno) Indelicato, an alleged Bonanno captain, who the prosecution says was involved in the July 1979 murder of former Bonanno boss Carmine Galante.

While one government attorney suggested that Persico could intimidate former associates with his "eyeball-to-eyeball" cross-examination when they testify for the government, the stocky Brooklynite was all charm in his opening statement to the jury.

"Mr. Chertoff says this Mafia . . . is all about making money," he said. "I'd like to know where that money went. You won't see it coming to me . . . . They can't try me on gossip, on rumors . . . . You won't hear Ralphie Scopo utter my name."

Lopez, Persico's former attorney, said Persico decided to conduct his own defense "because he has a lot of charisma."

Persico, who has spent most of the last 14 years in prison and was recently convicted in another racketeering case, joked in a brief interview this morning, "I had a good attorney, but I just felt he was getting tired after all these years."