The prosecutor is so smooth and persuasive in front of a jury that defense attorneys who say they hate him concede he's probably the best courtroom prosecutor in Virginia.

A child-killer sentenced to prison for life asked the prosecutor, who had sent him there, to defend him on a separate murder charge in Florid. The prosecutor declined.

Fairfax Commonwealth's Attorney Robert F. Horan Jr., who has been on front pages and in television newscasts for two weeks as the prosecutor in charge of unraveling the mysterious death of Billy Viscidi, gets calls nearly every week from other Virginia prosecutors, asking how best to win convictions of murderers and rapists.

To the ruddy-faced prosecutor "there is no better time in the world" than when he's in the courtroom competing against a skilled defense attorney, fighting for a life sentence for a defendant charged in a multiple murder.

Horan's reputation extends across the state, according to Lewis Hurst, executive director of the Virginia Crime Commission. The prosecutor is "keenly listened to" by the Virginia General Assembly as an expert on criminal law, Hurst said.

With his courtroom finesse and his knowledge of Virginia's criminal statutes goes a manner called "hard-charging" by Horan's friends. His enemies, primarily defense attorneys whom Horan has gored in the court-room, call him, among other things, "unmerciful" and "cold."

Horan, 45, a compact Irishman who is a Roman Catholic and an officer in the Marine reserves, does not object at all to being called a hard-charger.

As Fairfax County's elected prosecutor since 1967, Horan has built a state-wide reputation as a prosecutor tough on drug users, burglars, murderers, rapists and -- when Sunday blue laws were still on the books in Fairfax -- Sunday shoppers.

Mark Russell, the comic who once was Horan's neighbor in Annandale, lauded the prosecutor for raiding drugstores on Sunday in u971 with county police.

"Because of (Horan's) diligence, our Annandale children might one day be safe in the sunshine of nonassociation with the unsavory types who would purchase a sport shirt on Sunday," Russell wrote in a letter to a newspaper.

Horan enforced the blue laws until judges refused to permit the prosecutions. He said he happened to believe the laws were good protection for the "low-income guy" forced to work on Sunday and to be away from his family. Anyway, Horan said, his job isn't to agree or disagree with the law.

"It is not my function to determine if the laws are good, bad or indifferent. My function is to enforce the law," he said.

Yet, when the prosecutor's personnal values coincide with a particular law -- as in the case with Virginia's tough drug laws -- defense attorneys say and police records show that Horan makes an extraordinary effort to send people to jail.

"Those who deal with marijuana are like poison ivy," Horan wrote in 1970. "They infect those they touch and many times they infect them terribly." In an interview last week, Horan said his feelings about drugs haven't changed at all: "I don't feel the junk kids are using can make them better human beings."

Horan built his reputation in the late '69s prosecuting drug offenders. In his first four years as prosecutor he delivered more than 500 talks on drug abuse. He once led a raid by four detectives on a McLean house to arrest a 19-year-old on marijuana charges.

The year before Horan became commonwealth's attorney in Fairfax, county police made 16 drug arrests. Four years later, in 1970, they made 322 drug arrests -- an increase of 1,900 percent partly accounted for by the increased drug abuse in the county with latter year. One of Horan's assistants prosecuted a drug case in 1970 in which a high school yoth was sentenced to four years in prison for possessing one one-thousandth of an ounce of hashish.

The prosecutor's reputation as a crusader against drugs gained him no toriety, but he keeps his profile high by personally prosecuting nearly every major criminal case in Fairfax, by fostering high drama in the court-room and by shrewd dealings with the press.

"He is a master at playing the press in the big cases," according to Phillip J. Hirshkop, an outspoken defense attorney who said that he "hates" the prosecutor but envies his courtroom skills.

In the celebrated Billy Viscidi case, in which a 12-year-old boy was found buried in his own backyard in vienna on Aug. 12, Horan has remained in the news, releasing a few details about the death nearly everyday.

The news accounts, always accompanied by Horan's name, have said that Billy's family will not talk to police, that Billy's family will talk to police and the investigation is looking at the "close-to-the-home" situation, that Billy's death is "unnatural and surrounded by bizarre circumstances." that Billy's mother could not have known about her son's death until his grave was found, that blood in Billy's house was apparently human, and finally that Horan knows who buried Billy but he won't say -- yet.

The prosecutor promised on Friday that there will be a "major announcement" in the case "soon."

Horan said last week that he is in the news because "that is the nature of the job," he denied, in response to a reporter's question, that his disclosures have been designed to put pressure on a possible suspect. But he did admit that slow development of the case may help solve it.

"Certainly time gives anybody who knows about the death more of an opportunity to tell police what they know," Horan said.

Horan, who said he believes a "taste of jail" is instructive for offenders, particularly drug abusers, has a standing policy of demanding juries in drug cases. Juries, according to Prince William County Commonwealth's Attorney Paul B. Ebert, tend to give stiffer sentences than judges in Northern Virginia.

Many defense attorneys say the policy "terrorizes" them and their clients, forcing guilty pleas from accused drug users who know they don't have a chance before a typical upper-middle-class Fairfax jury.

"The prosecutor uses the policy as a club to force guilty pleas," said John Zwirling, an Alexandria attorney who has had considerable success defending accused users and dealers. "I don't think Horan is a particularly merciful person."

The prosecutor responds: "The fact that I think somebody should go to jail doesn't mean I have no compassion."

Horan argues that those who've been in jail on drug charges are "The best emissaries we've got. They go out and tell other users. 'No drug in the world is worth 30 days behind the sticks.'"

The prosecutor, who relishes his tributes his self-discipline, his love of courtroom combat and his desire to win to his Irish father and the U.S. Marine Corps.

Horan grew up battling in an Irish neighborhood in New Brunswick, N.J. "He never backed down," said his brother, Richard T. "Butch" Horan, an attorney in Fairfax. At five feet, three inches and 115 pounds when he graduated from high school, Horan's refusal to step away from street brawls caused him some nasty beatings, he admits.

One of six children in the financially strapped family, Horan said he was imbued in his youth by his father's rules. "We knew what they were and what would happen if we went against them. My father was a physical man. He didn't hesitate to hammer you."

When Horan wasn't getting "hammered" by his father, his brother says that "Bob and dad would have heated discussions of the issues of the day."

Between his father and the Marines, Horan spent four years in college at Mount St. Mary's in Emmitsburg, Md. The years at college were softening, "too much of doing your own thing." he said, but the Marines were "helpful" in regaining his discipline and drive.

In "A Rumor of War," Phillip Caputo's book about Vietnam, the author says of Marine training, "We had become self-confident and proud, some to the point of arrogance. We had acquired the military vitues of courage, loyalty and esprit de corps, though at the price of a diminished capcity for compassion."

"That Caputo is right on the money," said Horan, who remains active in the Marine Corps Reserve as a lieutenant colonel.

After he got out of the Marines in 1958, Horan, who done some work in Marine courts-martial, opted for law school and attended Georgetown University. "It all came easy to him," said Horan's brother, who also attended Georgetown. "He is a quick study. One time through and he's got it."

The prosecutor's taste for public service, especially after a 25,000-vote victory in 1971 in his first reelection bid, as commonwealth's attorney, led him to seek higher office.

His pursuit of a seat in Congress from Northern Virginia's Eighth Congressional District ended in failure. He won the Democratic nomination, but in 1972 -- the year of George McGovern -- party liberals got a third candidate on the November ballot. The liberal, William Durland, and Horan split the Democratic vote and Republican Stanford E. Parris won the election.

"You can say that experience soured me on seeking higher office. I felt the Democratic Party had done a number one me," horan said.

Last year, Horan was considered a likely candidate for state attorney general. He decided not to run, he said, because the job didn't interest him much and he didn't have enough money to seek state-wide office. It's a rich man's game," said the prosecutor, who earns $46,000 a year in his current position.

Horan said he still may seek higher elective office, but claimed he's content for now with being a prosecutor who takes major cases into the courtroom and wins them.

The prosecutor said his predecessor told him that the time to get out of the commonwealth's attorney's office is when the bad days start outnumbering the good.

"I'm not even close to that," Horan said.