Joint police patrols have started along the troubled border of Prince George's County and the District, almost a year after top officials in both jurisdictions promised quick action to tackle the corridor's crime problems.

On Sept. 16, authorities began the initiative, which pairs District and Prince George's officers in the same cars. Police officials plan to use the patrols Friday and Saturday nights, when officers generally notice an increase in crime.

About three dozen officers have participated in the patrols, and more officers are expected to join the initiative in coming weeks, police officials said.

The boundary areas have long frustrated authorities. Police officers are generally prohibited from crossing into each other's jurisdictions unless they witness a felony in progress. Criminals jump back and forth across the border to avoid arrest, making it difficult for police to catch them.

D.C. police commanders said 23 D.C. officers and 12 Prince George's officers conducted the patrols Sept. 16 and 17. The officers made more than 40 arrests, most in the District, the commanders said.

Fewer officers were available last weekend because D.C. police were handling security for antiwar demonstrations downtown, police officials said.

Cmdr. Robin Hoey of the city's 6th Police District said the patrols are "allowing us to be very aggressive and let the criminal element know they can't run back and forth across the border" to get away.

Residents have noticed the new tactics, the commanders said.

"A lot of citizens were surprised to see us going across both sides of the line," said Cmdr. Joel Maupin, who oversees the city's 7th Police District.

Police are concentrating the joint patrols within a half-mile of the border, which has become one of the most dangerous areas in the region.

Most of the 125 killings in Prince George's this year have occurred near the border. More than half of the District's 128 killings through August occurred east of the Anacostia River, an area that borders Prince George's.

The new patrols follow months of inaction on the initiative by local and federal authorities.

Top officials from the District, Prince George's and the U.S. Marshals Service announced in October that they would soon start the patrols. The Marshals Service was to supervise the program and deputize officers, giving them authority to make arrests in each other's jurisdictions.

However, bureaucratic infighting and paperwork problems impeded the start of the program. The delay quickly drew criticism from D.C. Council members and community activists.

D.C. Mayor Anthony A. Williams (D) met with U.S. Attorney General Albert R. Gonzales in April and requested his help in getting the initiative started.

The Justice Department's Bureau of Alcohol, Tobacco, Firearms and Explosives took over the program. About 40 D.C. officers and 14 Prince George's officers have been deputized, police officials said.

Staff writer Allison Klein contributed to this report.

Prince George's County police officers who patrol near the District line and their counterparts on the city police force have been frustrated by the ability of criminals to escape arrest by moving back and forth across the border.