On the night that a street gang almost took his brother's life, Willie Herron stormed over to the scene of the crime carrying cans of paint. He chose a blank wall in an alley, and with the help of neighbors shining flashlights on his makeshift canvas, he labored feverishly well past dawn.

From his rage and grief came a seminal work of public art. "The Wall That Cracked Open" is what Herron called it, a haunting two-story portrait of how violence was tearing up Hispanic families like his in the barrios of East Los Angeles. It is one among thousands of murals here, all bright expressions of joy or pain that like nothing else reveal the soul of this complicated city.

But these days Herron's work, and many other murals across Los Angeles, are disappearing, victims of relentless graffiti taggers and, worse yet, oblivious county and state maintenance crews trying too hard to clean up after their mess.

"They have gone too far," Herron said one recent afternoon as he looked with dismay at the large smears of government gray paint that obliterate more than half of his mural, which had been hit by graffiti. "Works like this are a very important form of expression and identity for many of the cultures living here, and every day they are being ruined now for no good reason."

Anywhere else, the damage being done to the rough but vivid paintings that adorn the sides of buildings and freeways might be shrugged off as just another small sign of blunder and neglect by a big-city bureaucracy. But Los Angeles takes its street art quite seriously. The city bills itself as the mural capital of the country--some even suggest the world--so the latest reports of desecration to Herron's work and that of others are provoking serious uproar and debate.

For many here, the central questions of the controversy are difficult to resolve: How extreme should the city's fight be against the graffiti that gangs constantly use to threaten and taunt one another? Who should have the ultimate say over the fate of public art--the artists or the government?

The issue is an especially timely one because Los Angeles is becoming an ever more Hispanic city, filled both with reckless spray-painting Chicano gangs and with artists inspired by the traditions of renowned civic muralists in Mexico.

Earlier this month, the Los Angeles County Board of Supervisors joined the battle to protect murals around the city by ordering public works employees to be more mindful of the differences between community art and hateful scrawl.

Now, when maintenance crews come upon murals marred by graffiti, they will be required to ask questions first and whitewash their targets later. Public works officials are vowing to familiarize their anti-graffiti troops with the vast yet incomplete registry that nonprofit art groups in Los Angeles keep of murals. The county also is urging the state highway department to treat murals with more sanctity whenever they remove graffiti from the many freeway corridors here.

"This should be art that we treasure," said county supervisor Gloria Molina, whose district includes East Los Angeles. "People have lost sight of that."

But making the change may not be as easy as it sounds. Keeping track of new murals is difficult in a metropolis as sprawling as this one, and showing no tolerance for graffiti is a vital part of the city's long war against gangs.

Los Angeles spends more than $1 million a year in an elaborate campaign to remove gang graffiti as fast and as often as it appears. The city is so desperate to stamp out this method of communication for gangs that in some parts of town it has started putting its own artwork on public surfaces even before they get tagged. The city has spray-painted so many twisting green vines on buildings and alleys that any graffiti scribbled there would be hard to read, but some community leaders say that strategy is just as much of an eyesore.

"All of our efforts have been to get every wall that has graffiti completely cleaned up right away," said Dennis Morefield, a spokesman for the county's public works department. "So maybe there has been a lack of awareness among the workers we have out there about the artistic value that some of the murals have. But it's something we're trying to make sure won't keep occurring."

Another problem is that many of the murals are old, painted during the 1960s and early 1970s as raging forms of political expression in poor and disenfranchised communities such as Watts and East Los Angeles. Time, sun and smog have been brutal, and local art conservancies often lack the money to restore some of the most ambitious works, such as the half-mile-long monument to interracial harmony known as "The Great Wall of Los Angeles." Assorted artists have been painting it for two decades along a concrete flood channel in the San Fernando Valley, but it, too, is falling into serious disrepair.

Some murals also are less relevant now because the neighborhoods in which they were created have been transformed by new waves of residents. It is one of the facts of life in this multicultural metropolis. And to some newcomers, ridding streets of fresh graffiti is much more important than preserving fading murals from another time and a different culture.

"Communities change so much in L.A., and not every mural should be in place forever," said Adolfo Nodal, director of the city's cultural affairs department. "But we have to do more to save the ones that are truly important. It would probably be better just to leave the graffiti on some of those murals, because it looks better than those gray blotches they use to cover it anyway."

Some muralists are losing hope, though. And graffiti is hardly the only threat they face. Finding funding for public art is getting difficult, and property owners who once turned over their walls with delight to young artists often are more interested now in selling the space to corporate advertisers.

Those who have watched the mural movement in Los Angeles since its infancy decades ago say they fear that the aesthetic, which was once a powerful symbol on the streets of ethnic plight and pride, is slowly but surely being lost.

"We're trying to keep murals vital and alive, and there's a new generation out there that wants to paint them for their communities," said Judy Baca, director of the Social and Public Art Resource Center in Venice, which serves as a curator for many murals around the city. "But there's a lot that we're up against. And if we don't save some of these murals soon, it will be too late."

Some artists even say they are reluctant to keep painting around Los Angeles because they fear that anti-graffiti squads will erase their work. Herron, 47, has been busy this summer covering his mural with boards to prevent more damage.

It had been unharmed for 25 years, towering over the same bleak alley where his younger brother was jumped and stabbed with an ice pick, yet survived. As time passed, Herron had even come to believe that the graffiti on it helped illustrate the point he had tried to make as a young man about the senselessness of gang warfare. But no one asked his opinion about that before the mural was painted over, even though under California law artists are supposed to be notified well in advance of any changes possibly being made to their work.

Coming home to his old neighborhood in East Los Angeles is not easy now, for other murals he painted on walls and alleys there long ago also are vanishing.

An artist by trade, Herron still creates murals occasionally and is hoping to restore "The Wall That Cracked Open," but those plans are on hold until he hears more about the city's latest promises about how it will fight gang graffiti more carefully.

"This means so much me," Herron said as he stood mournfully before his lost mural, which featured two images of brothers, dripping blood, a grandmother holding a crucifix and abstract images for paths that lead to light or darkness.

"I was trying to say something important about what had happened to my brother that night and what was happening to our community--what is still happening. It's a shame that I have to do this just to save what's left. But enough is enough."

CAPTION: Willie Herron is boarding up "The Wall That Cracked Open" to prevent further damage by graffiti scrawlers and anti-graffiti squads.