CAMBRIDGE, MASS. -- Four months ago, Joyce Brown was living over a hot-air vent on a Manhattan street where she panhandled for cash, defecated and burned paper money given to her by passers-by.

Thursday evening, she was an honored guest at the Harvard Law School Forum, where she faced a respectful audience and a wall of television cameras as she delivered a ringing defense of the homeless in America.

"It's a pleasure to be here tonight," Brown said to a gathering that included about 200 students and advocates for the homeless. "It's a long way from 65th Street and Second Avenue." That was the site of a grate outside an ice cream parlor where she made her home for more than a year before she was the first of New York's homeless taken forcibly off the street and hospitalized under a policy of Mayor Edward Koch.

Hers is not a rags-to-riches story -- yet. But Brown, a one-time heroin user who raised a vigorous and highly vocal legal challenge to Koch's program of hospitalizing the mentally ill homeless, has become a kind of instant celebrity.

Since doctors released her from Bellevue Hospital on Jan. 19, Brown, 40, has become something of a spokeswoman for the homeless, appearing on television and lecturing at law schools.

Several New York reporters accompanied Brown to Cambridge Thursday, and a network television crew filmed her shopping in Harvard Square on the morning after her speech, "The Homeless Crisis: A Street View."

But Robert Levy, the staff attorney with the New York Civil Liberties Union who represented Brown, is troubled by the focus of the bright lights, he says, because they direct attention away from the problems faced by homeless people.

"When we elevate someone to this celebrity pedestal we lose sight of the homeless issue," he said. "The issue now isn't homelessness, it's did Phil Donahue give Joyce $300 to buy an outfit at Bloomingdale's?" In fact, the show did give her money so she'd have something to wear when she came on.

The larger society, Levy added, may be eager to transform Brown into a media star to assuage its guilt over the rising number of people living in the streets.

"It might be that we have to make her one of us so we don't have to think about what's happening to the homeless," he said.

But Brown clearly enjoys talking with reporters and says the attention will help the public realize that many of the homeless are sane, rational people who simply can't afford an apartment and are unwilling to sleep in public shelters.

"I like the press," she said. Then, laughing modestly, she placed her hand on a reporter's arm and added, "With my unique style, I think I will draw attention to the plight of the homeless."

At breakfast yesterday with three reporters and two Civil Liberties Union attorneys, Brown easily handled a barrage of questions about her drug use, her unhappy relationships with four older sisters (who fought to keep her hospitalized) and the New York doctors who diagnosed her as a chronic schizophrenic.

Brown, who is black, denied reports that she had often hurled racial epithets at black men on the street. And, after diverting reporters with a description of the ideal man, she returned to the business at hand.

"When I was on the street, I was disheveled and my clothes were malodorous," she said. "But now you see that on the inside I'm a totally different person."

In her speech, Brown told the crowd, "The main reason we have the homeless crisis is there isn't enough affordable low-income housing ... It's that simple."

Her attorneys -- Levy and New York Civil Liberties Union Executive Director Norman Siegel -- urged law students to help fight what they said was a growing trend among municipal officials to jail and hospitalize the homeless.

Joyce Brown's public saga began last Oct. 28, when workers with Project Help and the New York City police took Brown to Bellevue, where Brown said doctors drugged her and diagnosed her as a schizophrenic.

But throughout her 84 days of hospitalization, Brown insisted -- in lucid if angry terms -- that she was sane, and argued for her release.

In a highly publicized court case that civil liberties lawyers hoped would test the legality of Koch's program, a state judge discarded contradictory statements about Brown's mental health and ruled that, based on her testimony, she was "rational, logical, coherent," and free to return to the streets.

Acting Manhattan Supreme Court Justice Robert D. Lippmann also said the fact that Brown refused to be housed in a city shelter "may reveal more about conditions in shelters than about Joyce Brown's mental state. It might, in fact, prove she's quite sane."

Koch, in typical fashion, blasted the decision, saying, "If anything happens to that woman, God forbid, the blood of that woman is on that judge's hands."

But Lippmann's decision was overturned in a split decision by an appeals court, and Brown remained at Bellevue pending a resolution of her case. However, the Court of Appeals, New York's highest court, decided the case was moot when doctors at Bellevue released her after another judge ruled that Brown could not be forcibly medicated.

"The only thing wrong with me was that I was homeless, not insane," Brown said upon winning her freedom. "I need a place to live. I don't need an institution."

As of Feb. 18, Project Help workers had picked up 103 homeless people. Nineteen of them had requested court hearings to contest involuntary hospitalization, but judges had sided with only two of them, according to Suzanne Halpin of New York City's Health and Hospitals Corp.

Forty-seven were discharged, and 56 remained hospitalized at Bellevue or Creedmoor Psychiatric Center, a long-term state facility for the mentally ill.

Whatever the benefits or problems with Koch's program, the publicity surrounding Brown's case has been an embarrassment for the mayor, who personally singled out Brown for the Project Help program after speaking to her on the street.

Since being picked up in October, Brown has beaten the usually press-wise Koch at his own game by arguing her sanity and charming skeptical reporters.

In one instance, a New York television reporter who pointedly described Brown's street behavior in a televised interview was suspended by his station and later issued an apology to viewers.

According to family members, Brown grew up in a middle-class family in New Jersey and held a variety of secretarial jobs after graduating from high school and business school.

But she began using cocaine and heroin and lost her job in 1985. She lived on and off with family members, who complained about abusive behavior and finally asked her to leave. Later, Brown was convicted of assault and spent time in a New Jersey hospital, where she was diagnosed as psychotic.

Brown, however, called the diagnosis "a lie," and left New Jersey for the streets of New York City.

Today, Brown is living with a roommate at the Traveller's Hotel in Manhattan, a residence for single women with a history of homelessness that is run by a nonprofit organization. However, Brown wants an apartment of her own. "I want permanent housing," she said. "The hotel is transitional housing."

When she isn't looking for an apartment or appearing on television, Brown works on and off as a receptionist and secretary at the ACLU. She says she is searching for a full-time job in a different field -- "something working with people," she said.

Brown says she is also looking for love. "That's a normal, human emotion," she said. "When you're homeless, you still want love."