A federal jury began deliberations yesterday in the FBI's undercover "Brilab" case. Four men, including reputed organized crime figure Carlos Marcello, are charged with using bribes and kickbacks to gain state insurance contracts.

The jurors have heard 14 weeks of testimony in the conspiracy case. Besides Marcello, the defendants are Charles E. Roemer II, Louisiana's former commissioner of administration and once the second most powerful person in the state; I. Irving Davidson, a Washington lobbyist, and Vincent Marinello, a New Orleans lawyer.

Aubrey W. Young, a former state official, had been indicted, but U.S. District Court Judge Morey L. Sear acquitted him.

According to a 12-count indictment, the four agreed to engage in corruption to land state insurance business for two men who really were undercover FBI agents. Working with the agents was Joseph Hauser, a convicted insurance swindler who agreed to be an informer for the government.

"They did it willingly," said L. Eades Hogue, head of the organized crime strike force here, in discussing the defendants' willingness to deal in bribes and kickbacks.

Hauser had known Marcello before the alleged 1979-80 conspiracy was formed. Consequently, Hogue said, Marcello knew that "any dealings with Hauser were going to be bribery dealings. When he saw Joe Hauser, he saw money, he saw a wheeler-dealer, a man he was most familiar with."

Marcello is accused of being at the center of this alleged conspiracy, and in tape recordings played to bolster the prosecution's case Marcello bragged of decades of wielding clout in Louisiana politics.

Unlike the other defense attorneys, Marcello's lawyers did not deny that their client engaged in corruption. They claimed, however, that the agents entrapped Marcello.

They portrayed the 71-year-old defendant as a peace-loving man who wanted to be left alone. Defense lawyers branded the FBI's use of swindler-turned-informer Hauser as a pact with the devil, and accused undercover agents of lying, cheating and fabricating evidence.

Roemer was accused of accepting a $25,000 bribe in exchange for using his influence.However, he has claimed that he accepted the money as a campaign contribution for state Sen. Edgar G. Mouton during his unsuccessful gubernatorial race in 1979.

The government also claims that Roemer agreed to accept $43,000 as his share of the commission on the agents' insurance business.

But when he testified in his own defense, Roemer said the insurance proposals were ludicrous.

In its case against the other two men, the government has attempted to show that Marinello and Davidson had agreed to use their influence to help the agents get the insurance business.

According to the indictment, the agents gave Marinello $10,000 for then-lieutenant governor James E. Fitzmorris Jr.'s help. Fitzmorris has denied receiving the money, and Marinello's attorney has attempted to show that this payment would not have been illegal because Fitzmorris could be of no aid.

Throughout the trial, the jury, which was selected in a process that took nearly a month, has sat through testimony of witnesses and put on earphones to hear taped conversations.

Until Wednesday, they were allowed to go home each night, but once the final arguments began they were sequestered in a downtown hotel, and will shuttle between Sear's courtroom and their hotel rooms until they reach a verdict.