The very recent downturn in places such as Prince George's has raised hopes that the region is in the early stages of a historic decline in violent crime. But a similar dip in the 1980s turned out to be temporary.

Growth in juvenile crime and a coming bulge in the youth population could bode ill. By 1996, 25 percent of those arrested for violent crimes in the Washington suburbs were juveniles, up from 17 percent in 1990.

Criminologists warn that crime is a complicated phenomenon that responds to a web of social, economic and political factors, which in the Washington area include the great expansion and increasing density of the suburbs; growing pockets of poverty; and changes in family life and patterns of commerce.

Jonathan P. Caulkins, who builds mathematical models at Pittsburgh's Carnegie Mellon University to study the spread of crime, says that even if police and politicians did everything right, criminal activity "is still going to go up and down" because of factors beyond their control.

"We study crime like crazy and have oodles of theories, but in an objective sense, we don't really understand it," Caulkins said. "We don't have anywhere near the understanding of crime that we do of the behavior of subatomic particles."

24-Hour Suburbs

By 1980 the burglary rate in the communities ringing the District hit an all-time high. But as commercial centers grew and evolved, the growing crime was robbery, a violent attack on a person or a business.

By the 1980s, there were not only more bank branches, but also automated teller machines, dishing out cash at any hour. Over time, more copy shops and drugstores stayed open 24 hours, providing new reasons for people to be out late.

These tempting targets also were more accessible, thanks in part to new and wider highways such as the Prince William Parkway and Route 5 in Charles County, which made it easier for criminals to move quickly in and out of an area. The robbery rate rose 54 percent in Prince William and 154 percent in Charles between 1977 and 1997.

The rate of aggravated assault – defined as an attack meant to cause serious injury – rose even faster in many suburbs. One contributing factor was crowding and congestion; in Loudoun County, the assault rate rose 179 percent over two decades as once-rural communities absorbed 80,000 new residents. More established suburbs, like Montgomery County, also became denser as new housing developments and stores filled in vacant patches.

"Anyone who has children knows you tend to be a little crazy when you're all on top of each other," said Sharon Cox, president of the Montgomery Council of PTAs.

Reports of domestic violence – which account for a small but significant share of aggravated assaults – also increased as more police began treating such cases as crimes.

Meanwhile, the overall suburban burglary rate tumbled 53 percent, and other thefts also declined. The proliferation of home and car alarms played a part, as well as the spread of neighborhood watch programs.

Starting in the early 1980s, pawnshops had to furnish police with more detailed information about their inventory and clients. In the last seven years, such data have helped Montgomery police arrest more than 1,500 people peddling stolen merchandise.

By the end of the 1980s, though, suburban police were battling crack cocaine, which created a new class of violent addict and turf battles between rival suppliers. The drug acted as "a magnet that was drawing criminals out of other activities ... because the profits are so good," said Andrew Karmen, a criminology professor at John Jay College in New York.

Many heroin users also supported their addictions with crime. But crack produced a shorter high, sending addicts back to dealers more often and creating more chances for conflict. And some authorities believe that crack encouraged a shift from property crime to robbery because users needed money more quickly.

"People want what you have and they'll take it in a second," said Joan Fredericks, of Falls Church, whose husband was shot and killed in a carjacking in a quiet Fairfax cul-de-sac in 1993. "Because of drugs, people's attitudes have changed. ... It's not enough to steal anymore. They'll take your life, too."

Fredericks, 46, said she still suffers occasional sleepless nights. "It's so horrible being the person who is left behind," she said. "It constantly reminds you how vulnerable you are."

In Prince William County, the robbery rate increased 127 percent from 1986 to 1993, the heyday of the crack trade. Meanwhile, the burglary rate fell 26 percent. "The crack epidemic came on us, like most jurisdictions, like a tidal wave," said Police Chief Charlie T. Deane.

The wave also swept through parts of Prince George's County. A 1.6-square-mile section along Marlboro Pike near the District line became infamous for drugs and violence. In 1993, it was the scene of 115 robberies, 72 aggravated assaults and three homicides – including the death of 1-year-old Vania Zamba, who died in a fire set by five suspects trying to kill a witness to a shooting.

"You'd see guys hanging on the street corner. You'd see prostitutes," said county police Cpl. William Steen, who patrols the beat, known to police as H4. "It was a sense of out-of-control ... it was like the finger in the dike. Every time you turn around, there was another leak."

Unlocked Doors

Drive 30 or 40 miles outside of Washington and the contrasts are everywhere – sparkling town houses rise next to working farms; discount superstores dwarf aging main streets; new highways intersect with one-lane dirt roads.

Often, the new residents are hoping to escape urban ills such as rising crime. Many find that is not so easy, like the Rev. Daniel Lindsey, who four years ago moved his family from Prince George's to St. Mary's County in Southern Maryland.

"Everywhere you go, crime is following you," Lindsey said. "Most of us thought we were safe in our little haven, but that's not so." In 1997, Claudia A. Pickeral, 13, was killed three blocks away from Lindsey's new home in Longview Beach, and there were two arson fires – including one at Victory Temple Church, which Lindsey established.

Just north of St. Mary's, Charles County has absorbed 50,000 new residents in the last two decades. On their heels came chain restaurants and large discount retailers along Route 301 and Indian Head Highway and a major mall, the St. Charles Towne Center.

Crime came, too. Two decades ago, Charles had 23 robberies and assaults for every 10,000 residents. By 1997, the rate almost tripled, to 61.

"There's no question that an increased commercial presence is going to attract people looking for criminal opportunities," said Murray D. Levy, president of the Charles County Commission.

Levy said there has been a rash of armed robberies in recent years. In the spring of 1996, after a bank and a Taco Bell were hit in Waldorf, followed by a convenience store in La Plata, local authorities called in the Maryland State Police to teach businesses how to cut their risk.

Levy, 52, who owns a neighborhood grocery in Cobb Island, said that 20 years ago, neighbors rarely locked their doors because "you were the only one who would get locked out." But things have changed; in October, his store was burglarized.

Charles continues to draw people looking for moderate home prices and rural charm. "For people coming here from more urban areas, it's just heaven," Levy said. "But for people who have lived here 30 years it's not."

Police and criminologists said the violence in fast-growing places like Charles is characteristic of rural communities in transition. New communities often lack the social ties that protect older neighborhoods.

That's why the La Plata Crime Council has begun encouraging the 16 communities surrounding La Plata to form walking patrols. Council Treasurer Judy Melvin said residents of her 30-home community put a premium on learning about their neighbors. The mother of two knows, for example, that the man down the street has family in Pennsylvania, so she doesn't worry when a car with Pennsylvania tags shows up.

"But if there is some strange vehicle in the neighborhood moving really slow, you had better pass that information on, because they could be looking for it in another community," said Melvin, 46. "That's what it's all about, people working together."

The same kind of changes are taking place across the Potomac River. In Virginia's Stafford County, the population rose 152 percent in 20 years; the total number of violent crimes rose by 242 percent.

Twenty years ago, Stafford deputies devoted most of their prevention efforts to property crimes. Now, eight deputies teach free, 12-hour self-defense courses for women. The sessions have a long waiting list.

In both Charles and Stafford, sheriff's deputies say the size of their departments failed to keep pace with population growth. Last year, each Stafford deputy responded to more than 1,300 calls, up from 900 in 1986.

"The deputy here in Stafford knows he is handling twice the workload of any other deputy in the region," Jett said. "There is a sense of pride. But if you have one person doing the job of two people, something is going to get lost in the mix."

'Broken Windows'

That's what happened to Georgetown South, a community of 3,000 residents in the city of Manassas. The 1970s-era town houses deteriorated as their original baby boomer owners moved on to single-family homes and were replaced by poorer renters. Open-air drug markets and gang-related violence soon followed. In the early 1990s, Georgetown South accounted for 40 percent of all Manassas police calls, police said.

Throughout the suburbs, violent crime tends to concentrate in places like Georgetown South – poor, densely packed neighborhoods that have high turnover.

As more low-income people, including recent immigrants, have moved to the suburbs, such neighborhoods have expanded. Poor families usually live in smaller dwellings with less privacy, increasing the chances of conflict. They are less likely to have cars, so they are often walking late at night, criminologists say. Some immigrants become targets because they may not be schooled in which dangerous areas to avoid. And people moving to escape crime sometimes have ties to violent people from their past.

Crime also rises in areas that become dilapidated, according to the popular "broken windows" theory of George L. Kelling, professor of criminal justice at Rutgers University. Kelling says that when a neighborhood looks run-down, people feel less constrained to behave themselves.

Some suburbs also suffer from a spillover effect because they are easily accessible from higher-crime neighbors. Montgomery police say 11 percent of the people they arrest come from the District. In Prince George's, the figure is 15 percent.

Charles County Sheriff Fred Davis said that in a recent survey of the people in the county jail, half were not county residents. Twenty-two percent of them were from neighboring Prince George's, where crime rates are much higher.

"You have the easy route into the county. You have a high concentration of businesses and homes," Davis said. "It's so easy for those who want to commit crimes to shoot over the border" and then drive back to their own territory.

Sociologists also say that the number and character of a community's young adults can have a significant impact on violence. People ages 15 to 24 are more likely to be both victims and perpetrators of crime than older age groups, studies show.

The share of people in that age group has been shrinking in the Washington suburbs since 1980, so their numbers can't be blamed for the rise in crime, demographers say. But local police say the most troublesome youngsters are becoming more violent. Juvenile arrests for violent crime rose 70 percent from 1990 to 1996 in the Washington suburbs.

"Twenty years ago," said Robert F. Horan Jr., the longtime Fairfax commonwealth's attorney, "juveniles did crimes where adults were absent: car theft, the unoccupied dwelling burglary. Now you'll see more ... juveniles doing robbery."

Fighting Back

Howard County officials say their crime rate has dropped because of a steady influx of well-to-do residents, who participate avidly in community crime prevention efforts, and a police department that has grown along with the population.

When violent crime peaked in Alexandria in 1982, the city was Washington's most dangerous suburb. But the rate is down 42 percent since then. A large drop in the city's under-18 population since 1980 contributed to falling crime, officials said. But they also credit a well-funded police department, which has one of the area's most aggressive community policing efforts.

Beat cops in Alexandria are encouraged to crack down on nuisance crime and deal with burned-out street lights and graffiti. When community crime-prevention efforts faltered in troubled areas like the Samuel Madden Homes public housing complex, the department assigned officers to live and work there.

The department also focused on the problem of public drinking. Repeat offenders are jailed if they refuse to participate in an alcohol abuse program. Liquor stores are legally barred from selling to them; their pictures are posted by some cash registers. Arrests for being drunk in public fell 15 percent in the program's first two years.

"I don't think it's that we are doing any one thing right; it's that we are doing thousands of things right," Alexandria Police Chief Charles E. Samarra said.

In Prince George's, police and officials credit last year's 19 percent drop in violent crime to a slew of tactics, including training officers to confiscate firearms during routine traffic stops, and sending extra police to address crime patterns identified by a new computer mapping system.

The change in Prince George's is evident in high-crime areas like the H4 beat on Marlboro Pike, where the rate of violent crime has dropped 31 percent since 1991.

Steen, the patrol officer there, said that some drug dealers who used to plague the area are now in jail and that after-school programs and a police-sponsored sports league are keeping young people off the streets.

"We are still having a problem with robberies," Steen said. "The murders seem to have dropped. ... When I came in, the area seemed like it was all death and mayhem. Now, it seems to be isolated in certain areas."

Conservative scholars and many police officials contend that efforts to lock up more violent criminals for longer terms – such as Virginia's 1995 abolition of parole – have taken dangerous people off the streets. But liberal criminologists say the toughest sentencing laws tend to catch less dangerous offenders.

Studies that link incarceration rates to crime show that imprisoning many more people has some effect on crime. A 1993 study by the National Academy of Sciences found that tripling the U.S. prison population from 1975 to 1989 reduced violent crime by 10 to 15 percent.

Some factors influencing the current dip have little to do with law enforcement.

Crack use is falling around Washington, according to drug tests of inmates and emergency room patients. The growing acceptance of debit and credit cards at everything from grocery stores to gas stations makes robbery a less attractive crime because people are carrying less cash.

And some sociologists believe that the good economy is removing some incentive to commit crime.

The recent good news has begun to push crime-fighting down on the national agenda. In 1994, 31 percent of Americans told pollsters that crime was the most important challenge facing the nation. Last summer, 14 percent cited crime.

But the convergence of favorable factors might not last. "We should expect that some degree of crime is going to be with us for a long time, that crime does ebb and flow," said Caulkins, of Carnegie Mellon.

For instance, if one accepts the argument that a shrinking youth population and falling crack use are key reasons for the recent trend, the future may not be entirely rosy.

Both crack and powdered cocaine spawned spikes of violence as they became widely used, so the next new drug could do the same. And the area's population of 15- to 24-year-olds is about to shoot up again, as the children of baby boomers mature.

Most law enforcement officials are loath to predict what will happen.

"We're doing a good job of holding the line on crime, but we're holding the line in the face of a good economy and a temporary decrease in the number of young adults," said Edward A. Flynn, Arlington's police chief. "The challenge for all of us is to use these years of abating crime to prepare for the future."

Tomorrow: The Montgomery-Fairfax puzzle.