AYEAR ago, the street in front of Jerry Mofreh's north Chicago minimart was controlled day and night by dozens of gang members, drug dealers, pimps, and prostitutes. Mr. Mofreh would secretly dial 911, but when police arrived he denied calling for fear that gang thugs would beat him.
Today, Mofreh's sidewalk is virtually swept clean of crime. Thanks to a joint campaign by residents and police, Mofreh's business is up, his customers are no longer harassed, and police discretely respond to his calls. ''It's a lot safer,'' says Mofreh, who recently installed a floodlight above the notorious strip of sidewalk in Chicago's Rogers Park neighborhood.
Mofreh is one of millions of Americans benefiting from a downward trend in urban crime. From Chicago to Atlanta and Los Angeles to New York, the number of homicides dropped - sometimes sharply - in at least 10 major United States cities during the first half of 1995, according to a Monitor survey.
Overall violent crime also fell in many of the cities. While FBI findings show major reported crime has been declining nationwide since 1992, the abruptness of the latest reductions has surprised criminologists.
Experts say the falling murder rates in cities are a good barometer of safer streets because homicide is consistently reported to police. Up to half of all other violent crimes go unreported.
Still, the lull in violence is confounding experts. Possible causes, they say, include high-tech crime-tracking strategies, tougher law enforcement, and demographic shifts in crime-prone populations. Experts also differ over how long the slide in crime will last and whether punitive or preventative methods work best.
A front-page headline last week in the Seattle Post-Intelligencer read: ''Seattle's Six Weeks of No Killing; Even Detectives Can't Explain Welcome Absence of Violence.'' Along with a falling murder rate, the city is enjoying its longest homicide-free period in almost nine years.
''It seems everyone is seeing a decrease, and I haven't heard anyone come up with a reason why,'' says Los Angeles Police Department spokeswoman Lorie Taylor. Los Angeles saw a 20 percent dive in homicide in 1994 and another 9 percent drop in the first half of this year. Overall, violent crime dropped 12 percent and 6 percent in the same periods.
''Why is this happening? That's the $64 million question,'' says University of Houston sociologist David Klinger, a former policeman. Killings are down 32 percent in Houston so far this year.
Some experts attribute the trend to new, high-tech police tactics, such as computerized mapping of crime hot spots. Police target the areas with increased surveillance, stake outs, sting operations, and arrests of repeat offenders.
In New York, Mayor Rudolph Giuliani last week singled out crime tracking as a major factor in the city's sharpest ever drop in serious offenses - 18.3 percent in the first half of this year. Homicide plunged 31 percent, with declines in ''some of the toughest precincts in the city'' said Police Commissioner William Bratton.
New York's success is significant because it is the first US city to map crime so relentlessly, says University of Maryland criminologist Lawrence Sherman. The city plans to spend some of its $54 million in federal anticrime funds to boost the speed and precision of its electronic crime mapping.
In Chicago, an electronic mapping system launched last October already provides beat officers with up-to-the-hour crime maps on a daily basis. Police in Rogers Park recently used the system to halt a spree of burglaries linked to pawnshops.
Enforcing the law
Tougher laws and law enforcement have also helped curb urban crime, the experts say. Chicago's intensive arrest and gun seizure strategy has taken more than 20,000 guns off the streets each year and helped drive down the city's half-year murder rate by 18.5 percent. Drive-by shootings and shooting deaths have declined even more sharply, by 53 percent and 23 percent.
Chicago police have seized fewer weapons since a Jan. 1 state law made illegal gun possession a felony - a sign that criminals are keeping their weapons off the street. In New York, recovering firearms helped slash the number of killings from handguns by 40 percent from January to June.
''If we keep making more arrests and seizing more guns, I'm optimistic there will be less crime,'' says Professor Sherman. But there is a trade-off, he adds: ''It overcrowds the jails.'' Indeed, federal and state prisons are already 20 percent to 30 percent over capacity. The number of US prisoners has doubled to 1.5 million in the past decade.
A crime-fighting strategy based on harsh punishments could ultimately backfire, some experts warn. ''Building a humongous prison system and warehousing people will create a very large subclass that is unemployable,'' fueling more crime, says Hubert Williams, president of the Police Foundation, a law-enforcement think tank based in Washington.
Instead, these experts focus on the underlying demographic and social causes of crime. James Fox, dean of the College of Criminal Justice at Northeastern University in Boston, says he believes that the fall in crime is due to a temporary decrease in the number of teenagers and the mellowing of aging baby boomers.
But this short-term dip will soon give way to an explosion of murder, robbery, and drive-by shootings as the teen population surges, Professor Fox says.
''We're fooling ourselves by celebrating declines in the rate of crime,'' he says. ''The only reason the problem is manageable is that the number of teenagers has been dropping'' - a trend that is now reversing, he says.
Over the next decade, the US will experience a baby boom ''echo,'' with a 23 percent hike in the number of teens aged 14 to 17. Currently, this group of Americans is murdering at a faster-growing rate than any other. From 1985 to 1993, the number of homicides committed by youths aged 14 to 17 leapt by 165 percent; this compares with a 65 percent jump among those aged 18 to 25 and a 20 percent decline among people over 25.
''This generation of youths has more dangerous drugs in their bodies, more deadly weapons in their hands, and above all a much more casual attitude about violence,'' Fox says. The overall drop in homicide masks the fact that teenagers are increasingly the perpetrators and victims of murder. In Chicago, 32 percent of the homicide victims and 46 percent of the accused killers in the first six months of this year were under 21. A recent survey in Virginia found that young people were twice as likely as adults to have carried a semiautomatic pistol at a crime scene.
The surge in juvenile violence could be ''the front edge of a sharp spike that is going to create serious problems for America,'' says Professor Klinger in Houston. Youth programs are vital to countering the idleness and family breakdowns that can spur teen offenses and gangs, Fox and others say.
Staking out a middle ground between advocates of punitive and preventative crime fighting, some experts favor a holistic, hands-on strategy known as ''community policing.'' Dozens of cities are experimenting with the strategy, which shifts police onto the streets to ally with residents against crime.
In Chicago, an ambitious community-policing drive has put 1,000 more police on the streets. Launched in April 1993 and recently expanded citywide, the program has cut crime in five pilot districts including Rogers Park. ''The impacts in Chicago are among the most substantial I've seen in the country,'' says Wes Skogan, a criminologist at Northwestern University in Evanston, Ill.
Chicago's success has hinged on two factors: First, the program is department-wide, mobilizing all officers from beat patrolers to detectives. Second, police use special request forms to direct other city agencies to solve - within a limited time - crime-related problems ranging from abandoned buildings to graffiti, overgrown trees, and broken street lights.
''Granted a pothole isn't a police problem,'' says Rogers Park District Comdr. Thomas Byrne. ''But when a police officer writes a report and gets it fixed, he has credibility in the community. We didn't have a lot of credibility when we started this. We do now.''
That credibility, in turn, has enabled police to win support for their crime fighting from residents like shop-owner Jerry Mofreh. Mofreh, for example, tipped off police on how drug dealers hid drugs under their tongues in tiny plastic sacks and swallowed them when police approached. Two weeks ago, he says he helped police find a teenage runaway girl.
Backed by residents, community policing has cut crime in some of America's toughest neighborhoods, such as Englewood in Chicago and the Bronx in New York, as well as among the most crime-prone age groups. In Boston and Seattle, antigang police units, summer-job programs for ''at-risk'' youths, and ''anger management'' training at schools have worked well. Boston last year achieved a significant drop in youth crime.
Despite the gains from such programs, experts stress that no single strategy has proved decisive in reducing crime. Among cities with strong community policing, for example, Kansas City, Mo., saw homicides plummet 32 percent in the first half of 1995, while in Phoenix murders increased 25 percent.
''There are no magic formulas,'' says Mr. Williams of the Police Foundation.
Still, one can glean the hint of a long-term solution in the determined look of Sharon Endo, a slight figure wearing an orange arm-band and armed with a cellular phone, as she patrols Chicago's Morse Avenue with fellow residents three or more nights each week.
When Mrs. Endo and other volunteers started their patrols last April, gang members hurled cherry bombs at them and blocked their path by overturning garbage cans. For years, the gangs had scared off shoppers and harassed storekeepers out of business.
''We called the police, and they soon stopped,'' Endo says. In the first year of community policing, robbery, burglary, and theft in the Morse vicinity fell by 72 percent.
''The police can only do so much. We take up the slack,'' Endo says.