BOSTON — JENNIFER WEXLER knew exactly what to do when a man tried to grab her purse one night while she was walking alone on an unfamiliar Boston neighborhood street.She got out her special crime-alert whistle and blew it as hard as she could. Neighborhood residents poured out of their homes and came to her assistance. Someone phoned the police while others tried to track down the man. Residents then directed police to the man's location and he was soon apprehended. For Ms. Wexler, who is active in a different crime-watch group where she lives, the experience is convincing proof that communities coming together can help fight crime. "I can hardly express with words ... this really wonderful sense of just caring, that people came out to help and they didn't have to. They heard that whistle and they responded. This crime-watch thing is working," Wexler says. Law enforcement officials around the country are striving for this kind of successful community police work. One emerging trend is "community policing," in which, through supporting crime watch groups, putting officers on beats, or setting up new neighborhood police stations, local police reach out to their communities. Such efforts at the local level come in response to a continuing wave of violent crime in US cities with little government funding or support. States and cities from Massachusetts to California, struggling with tight budgets and limited federal leadership, are searching for solutions to an escalating number of violent crimes and drug-related homicides, say law-enforcement officials. The problem is severe in urban areas, where youth gang violence plagues city streets. According to 1990 Federal Bureau of Investigation crime statistics, the number of juveniles arrested for murder, rape, robbery, or aggravated assault in the United States increased by 38 percent from 1986 to 1990. Criminologists say juvenile violence will only increase unless strong anticrime measures are initiated. And many say solutions lie in long-term, preventive measures that involve community participation. But neither the federal government nor state governments have done much in this area, says Barry Krisberg, president of the California-based National Council on Crime and Delinquency. States have pushed few anti-crime initiatives forward, Dr. Krisberg says. "I think the basic problem with the states is that most of them are broke; facing deep deficits, making savage cuts in programing," he says. "I see most trying to hold the line on basic operations." Local law enforcement officials fault the federal government for providing little leadership, funding, or research. Gil Kerlikowske, police chief of coastal Fort Pierce, Fla., says the federal government needs to adopt more community-based preventive strategies. "What I see are quick-fix answers and things that sound good to the voting population," Chief Kerlikowske says. "I don't see any response from the federal criminal justice level for this kind of [preventive] help, so we're doing it ourself." This climate of self-reliance has forced Kerlikowske and other city police chiefs to think creatively. Police in Fort Pierce - a distressed city with high-crime areas - have made inroads by setting up a new neighborhood patrol station. Police use the building as a community contact point and residents use it for crime-watch and Boy Scout meetings, and AIDS-prevention classes. Kerlikowske says such community-based efforts have helped reduce city crime. Last year in Fort Pierce there were 19 homicides, while this year there have only been nine so far, he says. In Peoria, Ill., the city police department is decentralizing so officers can work closer with the community. For example, instead of working in shifts, command officers act as managers of neighborhood zones 24 hours a day. Lower-ranking officers also are given more authority to make decisions while out on patrol. "It's getting out front before the crime occurs," says Peoria police chief Keith Rippy. "I don't believe [community policing] is a fad. I think it's a trend across this country, and I think we'll get better and better at it." In Wilmington, N.C., police will soon be using portable trailers for new neighborhood-based offices. The trailers will be stationed in high-crime areas and will be moved to different locations as the need arises. Police will be more visible in neighborhoods and they will not just "see citizens on the receiving end of a traffic citation," says Wilmington Police Chief Robert Wadman. Chief Wadman says prevention is a key to effective police work. He says long-term anti-crime initiatives should target troubled neighborhoods with high poverty and unemployment rates, he says. "The typical police organization is designed to react to crime ... but the primary mission is prevention," Wadman says. "The situation is going to take local initiatives to reach out and deal with it." The need is to target the younger generation, says Kerlikowske. In his city, an 18-year-old man recently was convicted of killing a police officer and was sentenced to death. The young man had a history of trouble with the local police dating back to when he was nine years old. "We all see the tragedy as not only losing the officer, but this tragedy of this 18-year-old who first came to the department's [attention] when he was nine," says Kerlikowske.