U.S. District Court Judge Walter L. Nixon Jr. knows the thrill of bagging big game.

The conference room of his Biloxi chambers, decorated with trophies from years of hunting and fishing, is nearly overwhelmed by a mounted blue marlin that arcs 12 feet across one wall. In its livelier days, it weighed 356 pounds.

Nixon, on leave from the bench, now has something in common with the marlin: During his trial here on charges of accepting an illegal gift and lying to a federal grand jury, an FBI informant referred to him last week as "the big prize."

Nixon, who was appointed in 1968 by President Lyndon B. Johnson, is the third active federal judge to be indicted for crimes allegedly committed while in office, and the trial has drawn a packed gallery of the curious and the history-conscious, despite testimony that is often contradictory, tedious and repetitious.

At the defense table in a small, second-floor courtroom where he is more accustomed to presiding, Nixon has sat almost motionless through 15 days of testimony. Federal prosecutors are seeking to prove that he accepted a sweetheart oil deal from a local millionaire and lied to a grand jury about whether he later tried to derail a drug-smuggling case against the millionaire's son.

His attorney, New Orleans lawyer Michael Fawer, is as voluble as his client is quiet, using breaks in the trial to offer sarcastic commentary on the weaknesses of the government's case. In opening arguments, he said he would prove that the case is "a sad lie," built on "blindness," selective culling of the facts and an informant who "thought of himself as the Dick Tracy of the week."

The government, Fawer said, "was simply hellbent to indict a sitting federal judge, and they weren't going to be turned aside."

Testimony indicates that in February 1981, Nixon paid Fairchild $9,500 for interests in three oil wells. Two of the wells have since returned $62,000 on the investment; the third was unsuccessful.

Prosecutor Reid Weingarten contends that the oil deal was offered by Fairchild in return for unspecified favors and accepted by Nixon as "a subtle, sophisticated use of his office . . . to get his hands on some of Wiley Fairchild's money."

Fairchild, a Hattiesburg millionaire, has pleaded guilty to giving the judge an illegal gift and spent two months in a federal halfway house. Paul H. (Bud) Holmes, a former Hattiesburg prosecutor, has pleaded guilty to reduced charges of contempt in exchange for his testimony against Nixon, once a close friend.

"I don't remember dates; I don't keep no notes," Fairchild, 73, testified last week. He said had no direct dealings with Nixon about the oil-well purchase and that a friend of Nixon's approached him about it, saying that "the judge had a bunch of kids in school and some of 'em were getting ready to go to college, and he needed a good deal."

Fairchild testified he did business with the judge "because he was an influential man. I believed if there was anything he could ever do for me, he would."

Beyond that, Fairchild's testimony was inconsistent. He testified that the wells were worth at least $26,000 in 1981 but said under cross-examination that the price was "fair" when the deal was arranged in 1980. He testified that he asked Nixon for help in his son's case and, under cross-examination, that he never asked the judge to intervene on his son's behalf.

Fairchild's son, Drew, signed a plea agreement in November 1980 in connection with the seizure of 2,200 pounds of marijuana at the Hattiesburg Muncipal Airport. George Phillips, U.S. attorney for Mississippi's southern district, said Drew was offered probation in return for his help in making the case against several other defendants.

Phillips said federal prosecutors told Drew in March 1981 that they were dissatisfied with his cooperation and would prosecute. Drew Fairchild was indicted on state charges in August 1981, pleaded guilty in 1982, later withdrew the plea and was convicted last year.

Wiley Fairchild testified at one point that he asked for Nixon's help in "late 1982" and that Nixon called him the same day, saying, "Everything is going to be taken care of to your satisfaction." Fairchild said Holmes, who was prosecuting his son's case, got on the phone next and said, "When this man Nixon tells me to do something, I don't ask no questions, I just do it."

In testimony last week, Holmes gave a different account.

Holmes said that Nixon "put in the good word" for Fairchild's son during a drive to Holmes' farm near here but that Nixon never asked him to do anything about the drug case. Holmes said he told Fairchild on the telephone that he would end the case against Drew but that Nixon "didn't ask me to do this -- I took it on myself."

Holmes said the call took place in May 1982, leading him eventually to put Drew Fairchild's case on hold before reactivating it in January 1983. On the witness stand Wednesday and today, Nixon said the call was made in March 1983.

Nixon said Fairchild had complained about Holmes' handling of the case without asking him to do anything. He said he "passed on" the complaint to Holmes but did not ask the prosecutor to do anything about the case. Nixon said Holmes immediately put in a reassuring call to Fairchild and passed the phone to Nixon, who merely extended his greetings.

"I was a victim of circumstance, really, caught in the middle between these two people," Nixon said.

Under questioning by Fawer, Nixon said that he did not consider the complaint or the phone call to be discussions about the drug case -- and that, therefore, he did not lie when he told a 1984 grand jury he had not discussed the case. The investigation began when a disgruntled former employe of Fairchild gave the Federal Bureau of Investigation a tip.

The trial is taking place here instead of Biloxi in part because Nixon's family is reknowned along the Mississippi Gulf Coast. In arguing against a Biloxi trial, federal prosecutors said jurors arriving for court there would "likely cross the Walter L. Nixon Bridge, named after Judge Nixon's father."

Because of the intense attention from the local news media -- newspapers have designed logos for the daily trial reports -- the 12 jurors and four alternates are sequestered in a motel. The same motel is accommodating the Washington prosecuting team and much of the out-of-town press.

Nixon's mother was raped and murdered in a celebrated Biloxi case before he became a judge in 1968, and residents follow the current trial closely.

Biloxi Mayor Gerald Blessey, pointing to recent federal "sting" cases, said there is some feeling among townspeople that the judge's case "involves forces at odds that go beyond this case and this town." There is skepticism, he said, about "whether this is a fair fight . . . . "

Sanford Steckler, a former state senator, is a Biloxi attorney who worked summers for Nixon and later joined his law practice. He said he fears that the publicity surrounding the case has been so damaging that "if he's acquitted, people here will assume he simply got off."

Closing arguments are scheduled to begin Saturday morning, and the jury is expected to begin deliberations later in the day.