A lot of people hope to leave their mark on society. But some take the notion literally, pack a can of spray paint, and just won't stop leaving their marks all over the neighborhood.
On New York City subway cars, graffiti have become a kind of guerrilla art form. In Los Angeles, it is a kind of primitive politics with real-life repercussions.
So Los Angeles is trying to wage a little war on the graffiti that infest some neighborhoods like crab grass - splotching every blank surface with defiant , highly stylized scrawls.
Late last year, City Attorney Ira Reiner attacked with a novel approach. He sued three gangs near the downtown area for graffiti, charging that graffiti are a public nuisance and that the whole gang is legally responsible for it as an unincorporated association.
So far, the plan has worked. A Superior Court judge bought the untried ''unincorporated association'' idea, and 65 gang members - under court order - spent five hours each in January painting over their own markings. Only four members refused to comply.
It is these four whose contempt hearings may bring about a legal test of the concept. Once the principles are established in court, the city attorney's staff plans to use the suit as a springboard for bringing bigger gangs before the bench.
Another strategy Mr. Reiner is considering is to hold parents responsible for the public scribbles of their teen-age children.
The catch is that these lawsuits are a slow and costly way to clean up a neighborhood's walls. The graffiti blight, however, is not just an aesthetic matter.
When a gang writes its name or initials on a wall, at some point a rival gang ''crosses it out'' with an asterisk-like mark. This is considered an affront; it marks a rivalry and sometimes provokes a new round of contentions.
''We use graffiti almost daily,'' says Sgt. Wes McBride of the street gang detail of the Los Angeles County Sheriff's Department. ''What we do is find out who's fighting whom by looking at new graffiti. The rivalries change weekly.''
Writing on walls is the chief way gangs have of flagging their turf - often a public housing project or areas of small clapboard or stucco houses not much more than several blocks across.
To each other, gang members are known as ''homeboys.'' They paint their gang's name, but often, too, their nicknames: Flaco, Wolfie, Sleepy, Smiley, and every neighborhood has someone signed Joker.
They are disciplined, formal graffiti as graffiti go, written in distinctive block-style letters using a well-defined language. Even in murderous feuds, they don't include obscenities.
And the feuds are often murderous. Sergeant McBride once heard a car pull away around the corner from a murder scene. There the victim's name had been crossed out in fresh paint and the name of the avenging gang written over it - a ready-made lead for investigators.
Officers can also keep regular track of new gang members by reading the walls. When some Los Angeles gang members vandalized a cabin near San Bernardino recently, they left their nicknames on their poker score sheets. The names and the homeboys themselves were easily identified from graffiti in their home neighborhood.
The Community Youth Gang Services Project - a two-year-old program to use former gang members to defuse gang violence - has made a continuous effort to persuade gang members to clean up graffiti. They work whenever paint is available and the gangs can be coaxed.
''If there're no graffiti, there's nothing to cross out,'' says Joe Quinones, deputy director of the project. ''There's no way to claim territory.''
Occasionally a gang member or even a local artist will design an elaborate wall mural on the side of a building. But when a mural goes up, he says, both sides of a rivalry respect it.