For David Luria, the cases come relentlessly, oppressively: A man in Southwest "beaten to a pulp" by a band of youths; a woman in Georgetown raped in a car; a small boy beaten and robbed; a teen-ager shot by another; a woman beaten badly about the face; a young man killed with a baseball bat.

David Luria prosecutes Juveniles for a living.

Once, almost nine years ago, Luria recalls, "I couldn't imagine a reason for an 11-year-old in handcuffs." A young, new attorney, he believed stories from clients he now thinks were guilty. When a client went to jail, it often upset him. Then he was defending juveniles and adults for a living.

But now he's traveled "some philisophical distance." He's "no longer idealistic," cynical about the system" and often "angry."

His appearance hardly reflects his attitudes. Of medium height and build, Luria, 37, single, affects a courtly, Old World manner. Faultlessly polite, he offers a seat with a nod and an extended arm. He's solicitous, almost apologetic - he'll wish it were a better day, or that he had more time. He wears three-piece suits and round, gold-rimmed glasses, a silver Navaho bracelet with a turquoise stone on his right wrist, and on his left a watch that runs 15 minutes fast "because I'm usually 10 minutes late for everything." He has a large puff of graying black hair, close beard and mustache. He was educated at Princeton. One colleague calls him "professor."

But "just below the surface" of his quaintly likeable exterior he's "angry because, as a prosecutor you always see the victim. You see the suffering, a person's life messed up." Sometimes, the victim is dead.

One case he will never forget: A boy who siphoned gasoline out of a car and poured it over a sleeping, elderly neighbor, then went for matches, lit one, and watched the man burn to death.

The boy was 6 years old, too young to prosecute.

Luria is in court, prosecuting a 16-year-old charged with selling drugs in a doorway in Northwest. The boy is handsome and immaculately dressed. His attorney recommends a dismissal.

The judge says, "I think the government (Luria) has proven its case." The boy places his hands behind his back as a marshal moves forward and slips handcuffs on him. He is led from the room.

In the hall, the boy sees the detective who arrested him and stops. "When I see you on the street," he says to the detective. "I'm gonna kill you."

"A lot of people call this kiddie court," says Luria. "They think it's all hubcaps and chewing gum." In fact, one-third to one-half of all serious crimes in the District are committed by juveniles (ages 7 to 18). Luria deals with minor offenses, but also with youths whose crimes range up to aggravated assault, rape and murder. One of 10 lawyers in the juvenile section of the D.C. corporation counsel's office, he handles some phase of 2,000 cases annually. In all, the city processes about 6,000 cases a year.

Prosecuting a juvenile is an expensive proposition: The cost of detaining a single youth for one year is $16,000, and the annual estimated cost of operating the corporation counsel's juvenile section (which many experts agree is badly understaffed) is more than $500,000. There are also costs for operating the court and social services.

"Juvenile court," says Luria, "is on the outer edge of the legal universe. This simply is not considered a prestigious job, but the lowest of the low." And it can be frustrating.

"The ultimate frustration," he says, "is that often the court doesn't do anything to these kids. The most any juvenile can be put away for is two years - even for murder. I've had just one person do two years. Actually, the odds are that a kid will never be detained. Maybe 15 percent are."

Luria says 95 percent of the juveniles prosecuted in the District are black. "When I first got here," says Barbara Flatts, a black juvenile prosecutor, "I was deeply hurt. You're really struck by the fact that most of the kids arrested are black. It's a painful thing to look at, unless you look at it from the point view of the victim. The victims are black and white - the defenseless, old or young. Our job is to protect the citizen. If, on the job, we can help a kid straighten out of his life, that's good."

Flatts says the youths, who often come from broken homes, view Luria as they do any white in the system - "as an authority figure, 'The Man,' but it's not personal." Of Luria, she adds that he is fair and has a good temperament for a prosecutor. "David's calm, controlled. He doesn't fly off like some."

"I don't believe every kid should be detained," Luria says, "or that every kid is guilty. What happens is you hear a lot of the same stories. You have to take each case individually or you lose you sensitivity." Day in Court

Luria's day, 8:30 to 4:30, is crammed sometimes with up to two dozen cases: If he is not actually prosecuting or deciding to, he may be in court, witness over the phone to come in to youth locked up on a detention center until trial; receiving a visit from a defense attorney who wants to get charges dropped; cajoling a potential witness over the phone to come into testify; taking testimony, or placating restless witnesses waiting around the court.

The unexpected:

A youth who had been found carrying a gun while on probation was standing in front of the judge, who was ordering him back to a juvenile institution. Luria, the prosecutor, was standing nearby, satisfied.

"All of a sudden," Luria says, "the kid gets by the marshal and runs across the room. I couldn' believe it. He comes right by me. I tried to stop him. God knows what would have happened if I did. All I did was fell his coat as he went by.

"There he went, head first, arms out in front of him, right through the window. He takes out the glass, the wood panes, everything. And we're on the second floor (in the old court house).

"Oh my God, I think, he's a goner. I run to the window and there he is out on the ground moaning and sobbing, on his back, face up, his legs and arms waving. The most amazing thing, he was released from the hospital one day later with no serious injuries."

The grim:

A 100-year-old minister is attacked in his Northeast home by two boys, aged 15 and 13. Luria says they asked for water but when they got inside they took the old man's money, about $3, and one got "a chain, like a dog chain, and garroted him. He was passing out when the other guy came out of the kitchen with a knife. That's all he remembered. He woke up in a pool of blood. Miraculously, he recovered." Finding His Way

Luria never expected to be a lawyer, and once he became one "never field, let alone the very byways of it."

He says his mother, who lives in Spain, "doesn't think too highly of my job. She'd much rather see me as a very successful lawyer flying off to London and Paris making deals. Or representing some celebrities." In fact, Luria's early years - emphasizing travel and the arts - seemed to point him toward a more exotic lifestyle than the one he happened into.

From age 8 to 13 he lived in Bermuda, then a year in New York City, then Watertown, Conn., where he attended Taft School. His stepfather was the late James Ramsey Ullman, a mountain climber an prolific author. One of his books, "The White Tower," was a 1946 best seller. He also served as historian on the first successful climb of Mount Everest by Americans. Luria followed in his footsteps to Princeton, but no further.

WHen he graduated in 1963, Luria didn't know what to do. He took a number of jobs. At one New York public relations firm, he says, "I was typing away and the marshal comes in and puts numbers on the furniture.That company moved overnight, to a hotel room.

"I spent much of my time in a Hungarian bakery at Second Avenue and East 83rd Street, drinking coffee. And I got heavy into TV."

He worked two weeks in Bloomingdale's basement, just before Christmas. "At 9:30 in the morning, there were these hordes of old ladies with their noses pushed up against the glass. When the door opened, you had to step back to avoid the charge. 'Do you have the shower curtain in jungle green?' This was the lowest point for me.

"My parents would say, 'You don't have to practice law. Just go to law school. It opens doors. You know, the cliches of non lawyers. I hated law school." After Georgetown law school, he stayed on in Washington. A friend with the Public Defencers Service persuaded him to help with some cases. "I didn't feel ready for trials but one day . . ."

With a tremor in his voice (and at one point in the trial rendered utterly speechless by fright, Luria won his first case; his 18-year-old client was judged innocent of stealing a tape deck from a car.

He became hooked when he won his second case. "There was this fellow in a Connecticut Avenue bar caught with his hand in a girl's pocketbook. But he refused to acknowledge it. He said he was a stranger in town, he was lonely, maybe he ahd too much to drink, maybe his fumbling around gave somebody the impression he was stealing something. To my amazement, the jury acquitted him.

"Two in a row, I thought. Nothing to this. I'm a great lawyer. Then I lost five in a row."

But in 3 1/2 years as a defense attorney - handling both adult and juvenile cases - he won his fair share. Still, he says, "I defended hundreds of people and only a handful I believed were innocent. As a defense attorney, the last thing you want to get out is the truth. As a long-term thing, I didn't want to lead my life that way."

Luria has two posters on his office wall, one titled "West Virginia Owls" and the other "West Virginia Summer Birds."

Bird-watching has become an important part of Luria's life; it is among the diversions that help him endure the grimness of his work. He also teaches two law courses at American University, serves as a tour guide around Lafayette Square, and hikes. "It's very therapeutic," he says, "to get up on a Saturday morning and tramp around the woods lookinf for warblers."

Luria says most attorneys who do what ha does burn out after 30 months. "It's a steady, downhill kind of thing," he says. "It gets to the point you can't take any more misery." Psychc Journey

About five years ago he turned to prosecution, strictly juveniles. By that time, Luria's psychic journey was well under way; from a naive new defense lawyer, he has become what he calls a "hardened" prosecutor.

He says he's shed the "prevailing liberal, cocktail-party ethos in Washinton on the criminal justice system - over-sympathy with the guilty, not enough sympathy for the victim.

About his hange in attitude: "I don't think it was any one case. It's not a question of the heavens opening. It's an accumulation of incidents."

At first, his idealism collided with a "pervading cynicism" in the criminal justice system. He says even the judges can be cynical.

"I was defending this pathetic old guy who broke into a camera store. He turned himself in, said he wanted to go to jail. I asked for less than a year, that's all you could do. The judge says, 'Okay, 360 days' He had a big laugh at my expense. All the people in the courtroom guffawed." The Detached Outlook

Seeing him walking out of a courtroom with his head bent, hating to see his client go to jail, a colleague took Luria aside. "He told me, 'Where are you going tonight? You're not going to jail. Did you do everything you could? Then, don't worry. Go home and have a drink."

Luria says that "detached" approach helped him especially when visiting cellblocks to see clients. "It's appalling: I'd see these people in one cell. But after a while, you can go in and act as tough as you can. Sometimes defendants in cellblocks have fits, epileptic fits. I think the tension of the situation sets it off. The first time this happened I couldn't believe it. I'm interviewing a defendant, taking notes, and this guy right next to us has a fit. But after you see this a number of times, you expect it."

Luria once received three letters in a single day from a client, "each letter more threatening than the one before." By his last trial as a defense attourney, he says. "There weren't many illusions left. This guy robbed somebody. He told me he was guilty. Ethically, I counldn't put him on the stand but I 'walked' him, beat the charges. It didn't make me feel one bit good. On the one hand I had the satisfaction I was a good enough lawyer, but as a citizen it made me shudder to think theis guy would be back out on the street."

His "hardening" process accelerated as a prosector. He says getting to know the victims, the relentless grim stories, does it: "They tell you what happened, the shootings, cripplings, robberies. Even something small, like having your car stolen, can mess up your life."

But Luria says "the juvenile system is philosophically disinclined to incarcerate juveniles," that emphasis is put on "rehabilitation." Many juveniles, he adds, are repeat offenders, "recycled" through the system. Sometimes the system works. "I've had people at the detention homes tell me that some kids come back years later and thank them. But I think in most cases a kid is going to be rehabilitated only if he has some wherewithal - like a person who cares - outside the system."

Luria thinks there should be longer terms for "the dangerous kid" and "some kind of conformity among judges" on sentencing. He believes judges should be assigned to longer terms in the juvenile court and that one judge should be placed in charge of each Superior Court subdivision - steps, in fact, that new Chief Judge H. Carl Moultrie I recently took. "Now, a kid can go before five different judges at different stages of his case," says Luria. "It's a floating crap game." Fear

Fear is not his constent emotion, but there are moments. Two years ago Luria was brought up short while walking along M Street near Georgetown.

"A big strong kind of about 15 stepped in front of me.

"'Hey, he said. Then said it again. 'Hey,'

"Yeah: I said. This obriously was not like seeing an old fried.

"Don't you work down at the court?"

'Yeah.'

"'I thought you did. I've seen you there with those three-piece suits.'

"Have I had any of your cases?'"

"'Nah, hah.'"

The youth moved one and Luria breathed easier.

"It turned out that about six months before I had prosecuted him. I had argued and argued to keep him locked up. He was one of three guys who beat up a man. I mean beat him up badly, especially around the nose - so as to make it not easily repairable." Small Victories

"You have small victories here," says Luria, "and big defeats. People say. 'How can you stand it? Why do you keep wasting your time in kiddie court?' I say this: I enjoy being in court: I don't want to be in some office worrying about trucking rates for the ICC. I like dealing with people: you have to be something of a diplomat to get some people to be witnesses. But the main reason is, you do feel you're doing something.Granted, you can't put these kids away for any great length of time, six months and they'll be out, but at least it's something.

"It'd be dangerous for a prosecutor to think he's going to clean up crime in D.C. singlehandedly. You do what you can day to day.

"Sometimes I feel I'd be very happy in a rural setting. But you know, in a passage in Sherlock Holmes. Holmes muses that the hills hide more crime than the worst slums of London. On the one hand I think being a country lawyer would be perfect. But it may be just a fantasy."