The lanky prosecutor worried out loud about the effect of a 1,000-pound federal flea landing on the back of a bird dog. A defense attorney confided to prospective juror that his grandmother used to play a little bingo herself. The judge titillated the press corps he accused of seeking sensationalism by saying that he did not sell eggs and goat milk for a living.

The Southern expressions and folksy manners of the participants in the bribery trial of Alexandria Commonweath's Attorney William L. Cowhig often belied the tension and furious legal infighting last week in courtroom number one in the Alexandria Circuit Courthouse.

There, in the aging, high-ceilinged chamber where Cowing presented cases for the past five years as the city's chief prosecutor, he is fighting an accusation that he accepted $32,000 in bribes in exchange for his "exercise of discretion." According to prosecutors, Cowhig received weekly payments of $500 in cash from the biggest bingo operator in the city.

Underlying the first criminal case ever brought against an incumbent Virginia commonwealth's attorney was the question of the credibility of his chief accuser and former neighbor, Dirgham Salahi, and the interpretation of the reams of documents submitted, by the special prosecutor, Edward J. White.

Chief defense attorney Louis Koutoulakos told the jury in opening arguments that the four-man defense team was donating its services to Cowhig "gratis, free of charge... as a labor of love... for Billy."

White told the seven men and seven women (two of whom will later be designated as alternates) that Cowhig committed the alleged bribery because of "money, which he needed badly."

The lone prosecutor and four defense attorneys fought daily from 9 a.m. to 5 p.m., presided over by a judge whose nickname is "Thunder." The objections, denials, arguments, and rulings are couched either in the southern - flavored expressions of White or Circuit Court Judge Percy Thornton Jr., or the New York-smoked idioms of Koutoulakos and co-counsel Leonard B. Sussholz.

When the defense tried to get Thornton to dismiss the case because of a parallel federal investigation of Cowhig, White protested that the state investigation had been like a "bird dog on point... when a 1,000-pound federal flea," in the form of the FBI, landed on it.

Thornton, who told the jury on Friday to avoid reading newspapers or watching TV this weekend by "digging up the potato patch," denied the defense motion.

When the jury was being selected Koutoulakos wore an old brown sportcoat, introduced Sussholz as "Lenny," eliminated the "folks" who said they were overly prejudiced in favor of policeman, and made the remaining jurors feel comfortable with the man they would judge, "Billy Cowhig... I knew his stepdad," Koutoulakos told them.

As he established ground rules for press conduct in the trial, Thornton, a former CIA agent who attended George Washington University Law School told reporters he was not a "freak" or a "weirdo in from the country," His rules, barring interviews with witnesses before their testimony, or talks with anyone connected with the case in the hallways, were designed to ensure a fair trial, he said.

At one point, White protested that a defense attempt to get an early draft of a statement by Salahi was a "fishing and slander expedition... Would they like all my funny little yellow sheets spread on my living room floor?" he asked rhetorically.

Several times Thornton yelled at defense attorneys to stop making "extraneous remarks," and once he shouted at both sides to "Cool it! I can holder louder than anyone."

The jury remains constantly fascinated by the proceedings, leaning forward to hear better, grinning at the lawyer's antics, occasionally watching the man they may eventually decide to sentence to as much as 10 years in prison.

Cowhig sits quietly at the defense table, sometimes taking notes, or making a point with one of the four attorneys defending him. His face reddens occasionally when a potentially damaging statement is made, and he seemed exhausted Friday after a Virginia State Police accountant finished his testimony.

The defense will begin its case tomorrow and hs confidently predicted it can account for the apparent difference between Cowhig's salary and his expenses through legitimate sources of income. The largest single recurring expense cited by prosecution was the monthly $1,820 mortage payment for a small hotel in the Bahamas, which Cowhig has said he loves.