Tom Hoag doesn't like the idea of defending guilty people, but he knows it's part of his job.

"It does get to me," says Hoag, 20, who is spending the summer as a volunteer investigator for the D.C. Public Defender Service (PDS). "Talking with a crime victim, you see your family and yourself in this victim, and you realize that you're working for the guy who may have done it."

He recently interviewed a young girl who had allegedly been raped. "I had to ask her some really tough questions," says the clean-cut senior from Brigham Young University in Utah. "She was the same age as my little sister."

Hoag's experiences and concerns are typical among the 65 volunteers, mostly undergraduates, who help PDS's 40 lawyers in one of the city's most unusual summer internship programs.

The students collect statements from complainants and witnesses, reenact crime scenarios to check police reports and occasionally take the stand to present their findings. They are the extra eyes, ears and legs of the public defenders, who annually handle more than 1,000 of Washington's most serious criminal cases involving destitute defendants.

In return for long workweeks and sometimes hazardous duties, the investigators get gas money and a stark view of the criminal justice system from the inside out. Many plan to attend law school and want experience on the street. Others simply seek a new twist on the seasonal migration of college students to the capital.

They proudly distinguish themselves from more conventional Washington interns, "who sit in their Capitol Hill glass offices, all dressed up," as one PDS intern puts it. However, there's little talk among the investigators of committing their lives to the disadvantaged, and few say they will even consider the grueling career of a public defense attorney.

Instead, they say, their goals are largely personal--to learn, to do something "constructive" with their valuable time off from school.

"We're really doing something here, even if it sometimes raises questions in my mind," says Hoag. "If I were working in almost any other internship, I'd be stuffing envelopes."

The PDS volunteers spend most of their time interviewing victims and witnesses, gathering facts that attorneys use to shape courtroom strategy and advise defendants of appropriate pleas. It's often tedious work, telephoning people who turn out not to exist or visiting addresses where there are only empty lots.

Kerry Randall, for example, spent a week tracking down witnesses to an alleged assault in a housing project off Kenilworth Avenue NE, wasting most of her time "driving around in circles." She said she visited the area on a more recent errand and found that "people . . . finally started to get to know me and asked, 'Hey, when are you moving in?' "

The teasing question is particularly ironic because, like almost all of her PDS colleagues, Randall, a Bowdoin College senior, is white, well-dressed and clearly looks out of place in the poor and working-class black neighborhoods where the investigators do a lot of their work.

Ray Dennison, supervisor of the six-year-old program, says that most of the 800 internship applications PDS receives are from upper-middle-class white students who can more easily afford to take a nonpaying summer job.

"There's a lot of shock for people who are coming out of their college dormitory or fraternity or social club," says Charles Ogletree, chief of the PDS trial division.

John Marshall, a 21-year-old graduate of the University of North Carolina, says occasional risks "are part of the excitement," and recalls one incident in which fleetness of foot proved his most important asset.

The prosecution witness Marshall was questioning "got real huffy and said, 'I'll ask you politely to leave the first time, and then I'll throw you out.' There were about 10 people in the room, and it was quite disquieting. Let me tell you, we got out of there, and fast."

Marshall says that when he gets "scared in a tight spot, I do something like fake a limp--get their sympathy any way you can. Or be friendly with the kids on the street, and often they'll show you where the people are who you need to talk to."

"It's a matter of not letting yourself get psyched out," says Randall. "Half the time your fear is in your head--paranoia."

Still, the investigators' motto, according to Jim Lystad of the University of Pennsylvania, is: "Don't go to 14th and T and ask for a man named Slick."

Jill Grayson, a senior at the University of Michigan, describes a recent interview with an extremely nervous Anacostia resident who had accused a PDS client of robbing him.

"For the first hour, he wouldn't even look at us. He was telling us how he got beat up without even looking at us, in a monotone the whole time," Grayson says.

Using a technique recommended by PDS, Grayson says, she tried to ease the tension with small talk: "He had a 2-year-old son, and we said how cute he was, and the father really warmed up." After three hours, Grayson got her statement.

"They have a very high success rate," PDS staff lawyer John Dwyer says of the volunteer investigators, some of whom work for extended periods during the school year. "They win cases for us."

Steven Gordon, chief of the felony trial division in the U.S. Attorney's Office in Washington, agrees: "They provide PDS with excellent resources. It's considered a very prestigious outfit."

Mingling casually in the PDS office at 451 Indiana Ave. NW, the interns seem a friendly, upbeat group. They attend to jangling telephones, write memos to the lawyers they are working for and research legal statutes. Were it not for the shabby second-hand furniture, peeling yellow wall paint and distinctly casual attire, it could be an interns' workroom in any well-appointed Senate office. But there is an underlying concern for the serious issues raised by the job.

"You may feel lousy about what you're doing sometimes," says Hoag, "but there's always a sense that it's a crucial thing for someone in the system to do."

Of the alleged rape he investigated, Hoag says, "I have felt lousy about that, but I did get the statement. . . . The way I think about it is that the attorney and I are extensions of the defendant into the legal system--what he could do for himself if he knew what to do."

Like Hoag, Robert Majteles considers himself politically "conservative" compared to most of his colleagues at PDS and says he favors stiffer sentencing requirements and the death penalty. "I'm not here on a crusade to change what happened to some person that caused them to commit a crime," he says.

"But I think our system is the greatest there is, and the right to defense is part of it," says the Hamilton College sophomore. "You cannot protect everybody's rights all the time, but you can move in that direction, and this is one way to do it--to help the defense and prosecution to improve."

There are those who see the job differently. Says Jim Lystad: "This is sort of an extension of what I believe in--working for the poor, helping people." Yet he declines to say whether he'll continue doing public defense work after attending law school.

Lynn Ford, a recent Penn State graduate, voices the common argument that "PDS is important to equalize the system, which often seems weighted in favor of the prosecution, with the police department's resources."

Ford adds, "The office often defends the rights of a guilty person. The way I look at is if someone didn't do this work, the system would fall apart and the truly innocent wouldn't have a chance."

Tom Furlong, 24, a former PDS intern who recently testified in a case he had investigated two years ago, says he "learned a tremendous amount about the way criminal law works for real" and was disillusioned by the attitudes held by some defense attorneys.

"I don't see many people here at PDS trying to change the system any more than they're just competing within it, trying to play the game better than the other side and trying to win it," says Furlong."They're trial lawyers, after all."

Furlong, who will attend Cornell law school in September, adds that he has decided not to work in the criminal field, in large part because of his experience with the Washington public defenders.

Majteles, on the other hand, praises the PDS lawyers for doing "a tremendous job for everyone's good, not just their clients. He also emphasizes that the volunteers "are not obligated the same way as a lawyer to actually defend someone in court. . . . We collect the facts and leave other judgments to other people."

"There are two bad things that could happen in any case," he adds. "A guilty man can go free or an innocent man can go to jail. Of the two, the second is far worse, because it would change his life forever. We work against that."