Crimes reported to police throughout Maryland fell by 9 percent during the first six months of 1999, continuing a downward trend for the fourth year in a row, according to figures released recently by the Maryland State Police.

Police and criminologists attribute the decrease, which mirrors a nationwide trend, to a crackdown on repeat offenders, programs that put police officers in closer touch with the communities they patrol, and the thriving economy.

In the Southern Maryland counties of Calvert, Charles and St. Mary's, reported crimes dropped by 7.6 percent overall. When broken down by crime, however, the numbers show that rapes rose by 8 percent and arson increased by 22 percent.

In a breakdown of overall crime by county, Calvert reported an increase of 14.8 percent during the six-month period. Crime was down 10.8 percent in Charles County and 15.1 percent in St. Mary's. The increase in Calvert appeared to result mostly from a surge in robberies and aggravated assaults during the first half of the year.

Crime in Montgomery and Prince George's counties fell 13 percent and 11 percent, respectively, compared with the first six months of last year. Crimes in the Baltimore area and western Maryland fell 8 percent.

The overall crime figures refer to the number of reports for homicide, rape, robbery, aggravated assault, burglary, theft, car theft and arson. Statewide, homicides fell by 11 percent, rapes dropped by 16 percent, and car theft and arson fell 12 percent.

Adam Gelb, policy director for Lt. Gov. Kathleen Kennedy Townsend (D), who oversees crime issues in the state, said he attributes at least some of the decline to state initiatives that have focused on the relatively small group of repeat offenders who commit a disproportionately large number of crimes.

Such programs include more frequent drug testing of people on probation and parole, and teaming probation officers with local police to better enforce restrictions.

But Gelb noted that crime statistics also reflect changes in how much trust residents have in their local police and, in turn, how comfortable they feel reporting crimes.

For example, if a police department gains a reputation for treating victims of domestic violence with sensitivity, Gelb said, the number of assaults reported in that jurisdiction may increase simply because more are reported.

"In a lot of ways, you're recording police behavior more than actual crimes occurring," Gelb said.

Specialists in crime statistics also caution against comparing one county's figures with another's because, although police departments are supposed to classify crimes by standard definitions, it's not known whether all do. A purse-snatching that might be recorded as a robbery in one jurisdiction could be classified as an assault in another.

"Every county could be doing it slightly differently," said Henry Brownstein, director of the graduate program in criminal justice at the University of Baltimore and a specialist in crime statistics. "They're supposed to use the same definitions, but the definitions aren't always precise."

Brownstein said the statistics are most helpful as a measure of general trends within one county. Although the number of crimes reported can depend on everything from activity in local drug markets to the overall health of the economy--low crime generally follows low unemployment--Brownstein said police also should get credit.

More police departments are using computers and other technology to trace where crime is happening and then focusing on those areas. In Maryland, police work with community leaders in crime-ridden neighborhoods designated as "hot spots."

"Up until recently, criminologists used to think police didn't have much to do with crime trends at all," Brownstein said. "But now . . . they can track better what's going on and they're responding to patterns."