Henry E. Hudson is the prosecutor's prosecutor, the Sergeant Friday of the Arlington County courtroom--humorless, uncompromisingly moral, relentlessly prosecutorial.

In his three years as Arlington Commonwealth's Attorney, the 35-year-old Hudson has jailed prostitutes who ventured into the county from the District and Maryland, clamped down on the sale of X-rated home video tapes, threatened to take a cable TV company to court for airing the titillating Playboy/Escapade channel, drastically reduced plea bargaining, and quadrupled the average jail term of convicted burglars.

Under Hudson, the average number of prisoners in the county jail has jumped from 141 to 215, crime has dropped by more than 17 percent, and residential burglaries have dropped by 35 percent. And to the astonishment and outrage of local lawyers, Hudson even placed a fellow attorney under electronic surveillance after an accused male prostitute made an apparently groundless claim that the lawyer had tried to charge him for legal services that were paid by the state.

"Being a prosecutor is my whole life," says Hudson, who this year will face his first reelection fight for the $52,000-a-year job since 1979 when he ousted the veteran Democratic prosecutor who had been his boss. Or, as Hudson put it a few years ago: "I live to put people in jail."

Henry Hudson--pale, balding and exceedingly formal, a Republican, and a believer in the sanctity of the law--does not tell jokes in or out of court, does not read many books or watch television, does not have hobbies, take long vacations, nor spend much time with his wife and dog.

He works 13-hour days six and seven days a week, lets his wife Tara pay all the family bills, and goes with police to the scenes of particularly heinous crimes so he can observe the violence he hopes to describe to a jury. He has few close friends, most of them policemen, prosecutors and other lawyers.

Hudson's work and the unflagging way he has pursued it have won the youngest local prosecutor in the Washington area a cadre of supporters as well as a vocal core of detractors who say he lacks compassion and is too keen on imposing his morals on the community. "Hang 'em High Henry," he has been dubbed.

"He's a zealot," says Alexandria defense attorney William Moffett. "I think he thinks he is Arlington County, and that an offense in Arlington County is an offense against Henry Hudson."

"He's obsessed," says John Zwerling, another Alexandria defense lawyer and Hudson critic. "There are so many things that people need to be protected from, like violent crime and burglary--and he's got his people looking into other people's closets."

But as local Democrats begin maneuvering to unseat him this fall, Republicans say the style of Henry Hudson is uncommonly in tune with the new attitudes of Arlington's once-liberal suburbanites and that his job is likely to be secure. The Democrats, who are grooming a candidate of their own, concede that a successful challenge to Hudson will be difficult.

"I don't think anybody is firmly ensconced," says Arlington Democratic chairwoman Sharon Davis. "But I do think he is going to be a tough one to beat."

Arguing a $2.5 million cocaine case recently in Arlington Circuit Court, Hudson was in classic form. His shoulders hunched, his neck straining nervously against a tight, starched collar, Hudson spat out questions in a deep bass voice that occasionally cracked into a tenor. He scowled when defense attorneys made jokes to ease the tension.

By the close of the trial, Hudson was leaning over the railing to the jury box, fixing each juror with the glowering stare of a revivalist preacher and hammering away at the defendants' claims that they were the victims of a larger drug trafficking plot.

"Is it consistent with human experience that someone is going to hold someone at gunpoint and entrust them with $2.5 million worth of cocaine?" he stage-whispered to the jury. Then, in an indignant roar: "It taxes the imagination!" The defendants each got 23 years in prison.

"Henry knows where the jugular is," says a fellow prosecutor. "And he always goes for it."

That trait, say Hudson's supporters and detractors, is at once his greatest strength and his greatest weakness. The prosecutor's friends say his firmness deserves much of the credit for the drop in Arlington's crime rate, which has declined faster during the past year than that of any other major Washington-area jurisdiction.

"The word is out that he's not playing," says John Robinson, executive director of the Martin Luther King community center in the county's Green Valley neighborhood. "He's hard on all kinds of people, black and white. He is hard on drugs, but of course most people want that because drugs are destroying this country."

"He's a very good lawyer, very competent," says Arlington defense attorney Louis Koutoulakos. "He does his homework."

Other defense lawyers are less inclined to sing his praises. They charge that he has acted systematically to choke off the rights of the accused and lengthen jail terms--by limiting plea bargaining; by demanding that more trials be held before juries, which in Virginia customarily recommend longer sentences than judges are willing to impose; and by restricting the ability of defense lawyers to find out before trial what evidence the prosecution has against their clients.

They also hold Hudson responsible for the police department's controversial antiprostitution tactics, in which vice squad members make dates to meet prostitutes in Arlington hotels and arrest them after they arrive. Civil libertarians have charged that the practice comes close to entrapment and even violation of the federal Mann Act, which prohibits taking women across state lines for immoral purposes.

"Why Henry feels he has to import prostitution into Arlington is beyond me," says Jonathan Shapiro, an Alexandria defense lawyer and a former schoolmate of Hudson at American University. ". . . He's really got this thing about vice that's way out of bounds with reality."

Arlington police, with whom Hudson has spent many hours investigating crime scenes, don't agree. "I take deep exception with anyone who says he's trying to impose his morals on the community," says Arlington Police Chief William K. (Smokey) Stover. "He's trying to enforce the laws. If the citizens aren't satisfied with the laws, they should go to their elected representatives and change the laws."

Sitting one recent afternoon in an office adorned with photographs of hashish and cocaine seized in raids, Hudson said he has restricted plea bargaining in response to community demands. The prostitution arrest techniques weren't his idea, Hudson said, insisting that they take only a "miniscule" amount of his office's time.

And as for lengthening jail sentences--that, said Hudson, is one of his proudest accomplishments. "I have always been a firm believer that certainty of punishment is the backbone of any type of deterrence," he said. Convicted burglars, for example, are now getting an average of three to four years in jail, he says, compared to the eight-to-nine-month sentences that were the norm under the county's previous prosecutor.

Hudson's world is a straightforward one, embellished with few shades of gray. He sees his job as enforcing the laws as they are written, not interpreting them to suit himself. "One of the things people don't realize is that the legislature makes the laws on what are crimes," he says. "I don't just make these things up."

What that means, among other things, is that Hudson's office prosecutes about 50 people every month for possession of small amounts of marijuana for personal use. "I believe the abuse of controlled substances makes no productive contribution to our society," Hudson says. "I strongly believe that the abuse of controlled substances is physically and psychologically damaging to the user, and creates a clear and present danger to the community."

An only child whose parents are retired Navy employes, Hudson grew up in Arlington with high hopes of becoming a doctor. A poor college grade in organic chemistry doomed that dream, so he got a job as a deputy sheriff. Later, he attended American University Law School at night while working as a deputy court clerk.

Associates at the time say he didn't share the liberal, defense-oriented views of many of the other law students. "He's very Elliot Ness-like," says Shapiro. "We were in a class together called 'Legal Problems of the Poor.' I got the impression he thought it was supposed to be 'Giving Legal Problems to the Poor.'"

The years after law school found Hudson working as an assistant commonwealth's attorney under William S. Burroughs Jr. in Arlington and later as an assistant federal prosecutor in Alexandria, where he built a reputation for himself as an energetic young man eager to specialize in major drug cases.

"When everyone else in the office was going out to get a beer, Henry was writing out the questions for the next day," says William B. Cummings, the former U.S. attorney who relied heavily on Hudson to build a successful case against Alexandria massage parlor kingpin Louis Michael Parrish. "Henry was not the brightest person I had in the office, but he was methodical . . . . Compared to other prosecutors, he's a gem of a prosecutor."

Later, after Hudson's former boss Burroughs got swamped by public criticism over his handling of a celebrated double murder case, Hudson, the former Young Democrat, declared himself a candidate for the job. He received the backing of county Republicans and ran as an independent against Burroughs on a platform pledging to crack down on crime. He won with a 5,000-vote margin.

Friends say the victory was the realization of a life-long dream, adding that they don't believe Hudson has any aspirations for higher political office.

"I think Henry wants to do a good job -- he wants to succeed at what he undertakes," says Robert F. McDermott Jr., a Washington attorney who takes semiannual fishing trips with Hudson and a group of local police officers, lawyers and prosecutors who call themselves "The Hookers.

"I have not gotten the impression that Henry is one of those people who is driven by blind ambition and would walk over people to accomplish what he wants," says McDermott.

For his part, Hudson won't speculate about his future plans except to say that he probably will run again this fall. Beyond that he will only add that he doubts he could ever cross the line to work as a defense lawyer because he doesn't think he could "comfortably" dedicate himself to the acquittal of a perpetrator of a violent crime.

"I'm certainly not in the criminal prosecution field because I want to be wealthy," he says. "I'm in it because I enjoy the satisfaction I receive working with people."