Liquor stores. Seafood joints. People hanging out on the streets. For several blocks in either direction, it's hard to tell whether you're in the city or the county.

"Now we're in Prince George's," says Capt. Kevin Davis of the county police as he drives over Southern Avenue in Capitol Heights on a recent night. "And now we're in D.C."

The traffic lights are the clue, he says. In Prince George's, they hang from cables at intersections. In the District, they are fixed to street posts.

But Davis says the criminals know exactly where the border is, and they know how to work it. The corridor has become the most dangerous stretch in the region, the scene of the majority of the 86 killings in Prince George's County this year. Of those, just 11 have been outside the Capital Beltway, and 14 have been on the D.C. border or within a few blocks of it.

The criminals know how to dart back and forth to avoid police, who do not have arrest or other official powers on the other side of the line, except in extreme circumstances such as a homicide or carjacking in progress.

"These guys learn from an early age they can work the line like a dodge ball game," says Davis, executive officer for the chief of patrol services bureau. "They know where to stand and where to move to avoid getting hit."

Southern and Eastern avenues, which run along the District's southeast and northeast quadrants, separate the county from the city. Much of the border area has been troubled, crime-plagued turf for years, the focus of community activism and police initiatives.

But this year, violent activity along the corridor has picked up so significantly on the county's side that the number of homicides in Prince George's is about 21 percent higher than at this time last year. In contrast, the number of killings has dipped about 3 percent in the District.

Police have different theories about why violent crime is an increasing problem along the border and whether the proximity of the District to Prince George's is a factor.

Former D.C. police chief Isaac Fulwood Jr., who experienced a similar crime surge in the city in the early 1990s, believes that some of the county's problems stem from the District's systematic effort to raze and scatter public housing complexes. He said many of those residents, who can no longer afford to live in the District's increasingly expensive housing market, took their vouchers and moved to Prince George's.

Some of those low-income residents were raised in city neighborhoods that were steeped in violence and simply brought that culture with them to the suburbs, Fulwood said.

Former Prince George's police chief David B. Mitchell, who reviewed a map of the county's homicides during the first six months of this year, said the patterns reminded him of the early 1990s, when much of the violence was fueled by drug gangs operating in both jurisdictions.

But others disagree. D.C. Police Chief Charles H. Ramsey and homicide detectives said the killings do not seem to cross the boundaries as often as in the past.

"Crime is a localized problem," Ramsey said. "A lot of the homicides, in particular, are about retaliation or arguments. Those things tend to happen in places you live or frequent."

Ray Crawford, a D.C. homicide detective who was detailed to work in the Prince George's homicide office, said he has examined the county's killings this year and most others dating to 2000. Few of the killings seem connected to cross-border disputes or issues, Crawford said.

This year, he has found fewer than five that have a connection to the District. Going back to 2000, fewer than 25 cases might be linked to crimes, suspects or victims from the District, Crawford said.

In examining the homicides, Crawford said he found that the killings were similar to those in the District in one sense: the motives. "It's about retaliation or disrespect," he said.

"In the 1990s, they had an influx of killings because of cocaine trafficking," which fueled high homicide rates, Crawford said. "Now these kids are mirroring D.C. as far as they are not going to take any junk from one of their friends. . . . They want to be little gangsters. That is pretty much it. It's a whole different story now."

Whatever the causes, the homicide numbers have been steadily increasing in the past five years in Prince George's, mostly in border communities such as Capitol Heights, District Heights, Seat Pleasant and Suitland.

By contrast, the District's annual homicide totals have dropped steadily during the past decade. Since 1993, when 454 people were slain in the District, the number has dropped almost every year. Ninety homicides have occurred in the District this year.

In Prince George's, Del. Rosetta C. Parker's home in Chillum is separated from the District by only a few trees and a large building that houses the Archdiocese of Washington. Parker, who has lived in her house on Jefferson Street since 1967, said she found her community a "beautiful" place until recently.

Ever since a man who lived across the street was killed in May, she has been uneasy, and leery of her proximity to the border. "Up until that happened, I wasn't concerned at all," said Parker, 74, a Democrat who was elected to the General Assembly in 2002.

The neighbor, Alan Moss, 51, was found shot inside his Mercedes. The crime has not been solved. He is one of four people slain this year within three miles of her house.

Police say they have been unable to link any of the cases or to determine who the killers are.

Gloria Boddie-Epps, a member of the community civic association, moved into a home near Ridgecrest Elementary School more than 30 years ago. She still likes Chillum but has seen changes that concern her. In March, two men were shot in her neighborhood.

"You just hope and pray that when you leave your house that you return safe," said Boddie-Epps as she looked after her two small grandchildren. "It's my prayer every day."

Like the District, Prince George's County experienced a spike in killings in the early 1990s, reaching an all-time high of 158 in 1991. Police officials at the time said a substantial number of the killings in both jurisdictions were fueled by drug gangs operating in the District with "satellite" locations in the suburbs.

In response, Fulwood in the District and Mitchell in Prince George's created a temporary joint patrol program that teamed county and city officers in each other's cars.

The two chiefs said the joint patrols helped reduce crime and kept killers and other criminals from slipping across Eastern and Southern avenues.

"There absolutely were connections," Mitchell said. "It made a lot of sense to partner up."

Davis, the Prince George's police captain, said the difficulty of tracking transient criminals is one reason police have a hard time determining where a crime originates.

The larger issue, he said, is that county and city officers do not have police powers in the other jurisdiction unless a violent crime is in progress. "We are right next to a jurisdiction we have no authorization to go into, except in special circumstances," Davis said.

On a recent evening near the border, Prince George's police were chasing on foot an 18-year-old suspect who they believed had stolen a motorbike. The teenager cut to his right and ran, and officers caught him hiding in a ravine.

"All he had to do was run 300 yards that way, and we couldn't have chased him," Davis said, pointing left toward the city. "He would have been home free."

The District and Prince George's agreed last fall to set up a new joint program, to be coordinated by the U.S. Marshals Service. But bureaucratic wrangling and other problems stalled the program. Recently, the two departments signed agreements to conduct the patrols with the coordination of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives. Police officials said the patrols should start in several weeks -- 10 months after the chiefs announced their joint effort at a news conference.

Each side would have about 30 officers deputized, said ATF spokesman Mike Campbell.

"This will allow different agencies to work together and not have to worry about borders," Campbell said.

Prince George's police recently began paying off-duty officers overtime just to patrol the border area. The department took the action in March in response to high crime and a lack of patrol officers to effectively deal with it. The short-staffed department responds to about 1,800 calls for service a day, which leaves few officers available to patrol one of the region's neediest areas.

D.C. and Prince George's officers do work together at times. In early May, a carjacking suspect was fatally shot in the head in the District by county police after a car chase, during which officers zigzagged over the border and exchanged gunfire with the suspect. County and city officers were involved.

Davis said that once the cross-border partnership gets going, it will bring the agencies together.

"For now we're kind of waiting on the sidelines," he said.

Cpl. Cicale, a Prince George's officer who declined to give his first name, talks to a resident after the shooting of two men on Central Avenue.Del. Rosetta C. Parker (D), who lives near the D.C. border in Chillum, says she has been uneasy since a man who lived across the street from her was fatally shot in May.People mingle on the D.C. side of Southern Avenue. Many of the 86 killings in Prince George's County this year have occurred near the border with the District.