When Prince George's County police released the names and photographs of three alleged Jamaican drug gang members sought in the slayings of five persons in a Landover apartment Jan. 22, it looked like a breakthrough in the battle to stop the worsening Jamaican drug wars in the Washington area.

But a bigger challenge lay ahead. Even though police think they know who the killers are and where they might be, to make actual arrests authorities still have to find a way to penetrate the underworld that envelops and protects Jamaican gang members.

"It's difficult to locate them because they move around, like gypsies almost," said Assistant Chief Isaac Fulwood Jr., second in command of the D.C. police department. "They're organized -- and they're not organized -- which is what makes them so difficult."

Just over a month after the Landover slayings, D.C. police are confronted with similar difficulties as they investigate the Saturday night killing of two Jamaican women in front of four toddlers on Meridian Place NW. Authorities said that those homicides may have involved drugs but that robbery and domestic troubles may also have been motivating factors.

Authorities say it is not unusual for gang members to have a dozen aliases and a sophisticated array of fraudulent identification cards, making it extraordinarily difficult to identify suspects. Members are said to have a nomadic existence, lodging briefly at "safe houses" in more than a dozen cities in the United States and Canada, then moving on to establish new outlets for drug sales.

Even when police are able to establish a connection, Jamaican gang members are often shielded by a code of silence that few witnesses or lower-level functionaries will break.

Throughout the United States, law enforcement officials say that Jamaican gangs -- known as posses -- are the newest and most violent organized crime groups. Posses sprang from neighborhood family and political ties in island shantytowns and took their names from the spaghetti westerns still popular in Jamaica.

Officials say they know of 30 posses nationally and nine locally, and they say they can describe in detail how the posses operate. Still, prosecutions have been limited to individual members as opposed to an entire criminal enterprise.

In the Washington-Baltimore area, Jamaican gangs have been responsible for at least 60 killings and countless shootings since 1985, according to local law enforcement officials. Yet few of the cases have resulted in arrests and even fewer in convictions.

"If you're going to deal on a local level with a national problem, you're just spinning wheels. It takes a combined effort," said Sgt. Frank Shields, a detective in the Brooklyn, N.Y., homicide division, which has been investigating Jamaican gang-related crimes for years and is helping police on several local cases.

To better coordinate their efforts, local police and prosecutors have joined federal drug enforcement, immigration and firearms agents to investigate 21 cases, several involving multiple killings.

Further complicating the problem in the District, where most of the area's slayings have occurred, is the history of Operation Caribbean Cruise. The Feb. 22, 1986, D.C. police operation was expected to result in the arrests of hundreds of Jamaican drug dealers and seizure of huge caches of automatic weapons and illegal drugs. Instead, what was to be the biggest drug raid in the city's history netted only 27 arrests, 13 weapons and $27,000 worth of drugs.

A federal grand jury is investigating whether some District police officers warned some Jamaican drug dealers that they were targets of Caribbean Cruise. Additionally, some members of the Jamaican community sued the District government, claiming that Caribbean Cruise was "vicious and unwarranted attack on innocent members of the black community." That lawsuit is pending.

Some local and federal law enforcement authorities working on Jamaican drug gang cases say the failed operation still casts a shadow on the District's efforts to crack down on Jamaican drug dealing.

"Because Caribbean Cruise had blown up in their face, police in D.C. put Jamaicans on the back burner," said a suburban prosecutor, noting that until the abortive drug sweep, police in Montgomery and Prince George's counties worked closely with their District counterparts on Jamaican cases.

"We've done everything we can to target Jamaicans," D.C. Police Chief Maurice T. Turner Jr. said in an interview yesterday. "The allegation that police officers tipped {targets of Caribbean Cruise}, we haven't been able to prove. That still hasn't stopped us from aggressively attempting to infiltrate the rest of the Jamaicans that are selling . . . drugs."

In October, D.C. police officials were unaware of Operation Rum Punch, a nationwide sweep involving federal agents in more than a dozen areas, including the District, Prince George's County and Baltimore. More than 150 Jamaicans were arrested on drug, homicide and weapons charges. Local police helped federal agents in making arrests in all the other cities, according to federal officials. But when asked by a reporter that day about the operation, District police officials said they did not know about it.

"We're not interested in whether it's Jamaican, Hispanic or black," said District police Inspector Nelson Grillo during a recent interview, explaining why city police had avoided joint investigations targeting Jamaican drug activity. "We're interested in . . . criminal activity, and we don't care what ethnic group is behind it. That focus is too narrow."

Shortly after that interview, D.C. police officials announced that they were joining a Jamaican Task Force with the U.S. Park Police, the U.S. Drug Enforcement Administration, the federal Bureau of Alcohol, Tobacco and Firearms and the federal Immigration and Naturalization Service.

This account is drawn from interviews with dozens of federal law enforcement authorities and local police in several jurisdictions and from examinations of official intelligence reports and court documents. All of them emphasized that the vast majority of Jamaican-born people living in the United States, including the community of 10,000 in the Washington area, is law-abiding.

In the early 1980s, in the wake of a violence-wracked election in Jamaica, posse members began coming to the United States, legally and illegally, setting up drug distribution networks for Jamaican-grown marijuana, said law enforcement officials. Since 1985, the violence has escalated as posse members have switched from marijuana to the more lucrative distribution of cocaine and guns. Officials said that posse leaders in New York and Miami have dispatched hundreds of small street armies to set up beachheads for drug sales in poor neighborhoods in places as diverse as Kansas City, Mo., and Montgomery County.

"Cocaine is more inherently violent," said Bob O'Leary, a former special agent in the Washington area for the Drug Enforcement Administration who now works for the INS. "Whereas marijuana stupifies, cocaine excites and makes for paranoia."

In the past three years, federal authorities say, they have identified 30 posses with thousands of members responsible for more than 600 slayings in cities from Boston to Los Angeles.

It is the violence that has made the investigations urgent. "I've never seen a group splatter themselves like the Jamaicans do," said INS Senior Special Agent William D. West, coordinator of the Mid-Atlantic Organized Crime Drug Enforcement Task Force, which covers the District, Maryland and Virginia. "They actually try to take people out in public places. They don't care if innocent people get hit in the cross fire."

In the worst local killing, four men and a woman -- all Jamaicans -- were shot to death in a Landover apartment Jan. 22. Police say they have linked three of the dead men to the open drug markets in Mayfair Mansions and Paradise Manor, two Northeast Washington apartment complexes that were among the first Jamaican-run crack peddling operations in the area. The three suspects are Jamaicans from Brooklyn, as were four of the victims.

Brooklyn North homicide detectives, who attribute a 25 percent increase in homicides in their borough last year directly to activity related to crack, refer to the franchising of the cocaine business as "McCrack."

Crack -- cocaine that is processed into "rocks" and smoked -- was introduced about three years ago in New York and Miami, where, at $5 to $10 a vial, it is cheap and easy to find. But in Washington, where the hallucinogen PCP has been the drug of choice for years, the same vial of crack sells for $25 to $30 and has not been as readily available.

That has brought a drug war to Washington.

"There's a simple reason. Dope is cheap in New York. Dope is expensive here. Buy your dope in New York, bring it here and sell it," said Prince George's County police Detective Mike McGraw, an intelligence and vice officer. "But when you're an outsider, you have to cut yourself a piece of the territory that's already owned by someone else. How do you do it? You start shooting."

Police sources said the following slayings in the District in the past 13 months resulted from a frontier code of justice among Jamaican drug gangs:

On Feb. 4, 1987, three Jamaican men argued over drugs in an apartment at 2950 Second St. SE. Roy Davis pulled a gun and shot to death Robert Newman, 22, inside the apartment. Then Newman's brother, Paul Newman, 23, allegedly fatally shot Davis.

On June 9, Vivienne McPherson, 26, Davis' pregnant common-law wife, was fatally shot in front of 2842 Robinson Place SE by an unidentified man. Police said McPherson had taken over Davis' drug business after his death and had invaded another dealer's territory.

On June 29, in what police described as an apparent retaliation for McPherson's death, two Jamaican men -- John Kitt and Leon Spencer, of unknown addresses -- were shot to death in front of 4300 South Capitol St. SW.

On Jan. 20, Horrace Lawson Pinnock, 34, a Jamaican from the Bronx, N.Y., was fatally shot inside a third-floor apartment at 625 K St. SE. Police sources said they believe that Pinnock's death was related to McPherson's slaying seven months earlier.

In the District, at least seven of January's record-breaking 37 homicides involved Jamaicans as victims or shooters, police said. They said that about 20 of the city's 228 slayings last year involved Jamaican victims. But they acknowledged that with 89 of the homicide cases still unsolved, it is impossible to know how many involved Jamaican attackers, a problem shared by other police departments.

In Prince George's County, nine Jamaicans were slain last year, compared with three in 1986. Among Montgomery County's 18 homicide victims last year was a 23-year-old Jamaican from New York who had been shot once in the head and left in a burning car. The body of his 20-year-old cousin lay 12 miles away in the District, shot in the head three times. Police believe that the two were executed for trying to sell drugs in an area claimed by another Jamaican dealer from New York.

In Northern Virginia, there are spotty problems involving Jamaican dealers, according to law enforcement authorities. But there has been a recent spate of shootings, none of them fatal, and 25 weapons were seized in rural Winchester, where young Jamaican men hawk crack on the streets of some neighborhoods, according to federal agents. In nearby Charles Town and Martinsburg, W.Va., last year, there were four Jamaican drug- related homicides.

Jamaican youths are lured out of the poverty of their island home with the promise of easy money, according to officials. Posse leaders furnish airline tickets, weapons, drugs and money to workers they recruit from large Jamaican communities in New York or Miami or whom they smuggle in from Jamaica, officials said. The workers, who know little of the overall organization of the posses, are promised commissions on crack sales, are given sales goals, and then are sent out to start crack outlets.

They peddle crack with the promise of joy and guarantee of addiction. It is a sound marketing strategy, enforcement officials said, because crack is so highly addictive -- and the high is so pleasurable to the smoker -- that what starts as a $25 kick can lead rapidly to a $600-a-day habit.

"They say, 'Take all the sex you've ever had, all your birthdays, all your Christmases, all the good things that have ever happened to you, and it don't come close to a crack high,' " said John Rainey, a Brooklyn homicide detective. "They made cocaine affordable to a certain economic class . . . just like computers started out in the thousands {of dollars} and now they're a couple hundred, just like VCRs."

Officials compared the Jamaican posses to the Italian Mafia in its earlier days, but they noted many differences. Italian mobs had fewer members but trafficked in much larger quantities of drugs. They did not get involved in street sales. The posses have many more members, who are more widely dispatched and sell much smaller quantities at the street level, keeping all the profits in the organization.

Often it is the newest members of posses -- those sent to an area to carve out drug territory -- who are killed, police said.

"There are only three or four likely scenarios" in any drug-related slaying, said detective McGraw. "Number one, it's a ripoff of drugs or money, which could happen almost randomly. Number two, it's rival dealers," he said. "Number three, it's dissension within the group. These people will shoot you in a heartbeat."

In the early 1980s, law enforcement authorities here and elsewhere began to notice a pattern of public shootings between competing gangs of young Jamaicans who they believed were selling marijuana. Early violence here centered on upper Georgia Avenue NW and in the Chillum area of Prince George's County, but since it has invaded all quadrants of the District and Montgomery County, according to police.

Federal agents first identified the posses in 1984, when international police asked the Bureau of Alcohol, Tobacco and Firearms' Miami office to help Jamaican police trace a cache of weapons seized on the island. Agents traced about 40 weapons to South Florida gun shops and linked other weapons to drug and homicide cases involving Jamaicans in several cities.

Federal agents began to uncover other posses with links to New York and Miami that operated in other cities, according to officials. Their methods of operation were strikingly similar.

Women in the groups rent apartments, buy cars and pay bills. Telephones with services such as call waiting, three-way calling and speed dialing are used extensively, and numbers are changed frequently, according to police.

Men in the groups move into a neighborhood to start a franchise and frequently pay off residents in money or crack to use their apartments for drug sales, a pattern D.C. police first noticed last summer.

Washington area police said they do not know how many crack houses are operating here, only that the number is increasing with the popularity of the drug. "A crack house can be an apartment with a family one day, a crack house the next day and a family home again," said one vice officer.

Armed with aliases, two or three sets of false identification and automatic weapons, posse members move from city to city. "It seems like there's an endless supply of 20-year-olds they can bring up to fill {posse} positions," said Montgomery County Detective Catherine E. Stavely.

Witnesses seldom cooperate with police. "It's like the code of the Old West: You don't testify against each other," said U.S. Park Police Sgt. Thomas P. Moyer. "You settle wrongs among yourselves."

Unlike Colombian cocaine importers who are primarily wholesalers, Jamaicans buy cocaine from South American dealers, process it and distribute it on the streets, according to federal agents.

For example, Colombian dealers may pay $15,000 for a kilogram of cocaine and sell it to Jamaicans in southern Florida for $25,000. Jamaican posse members distribute the cocaine piecemeal to supply depots in New York or Miami. From there, they move it to stash houses in various cities, where smaller amounts are sent to crack houses and street dealers. By keeping the cocaine within the organization, the posses can sell the $25,000 kilogram on the streets and in crack houses for $125,000, officials said.

"What you have here is a real violence-prone, extortion-oriented, organized crime group that can move into a neighborhood or an area, take it over {and} terrorize the inhabitants, who are generally from defenseless strata of society anyway," U.S. Attorney Joseph E. diGenova said in a recent interview. "And then they move on, after murdering any rivals in the vicinity, to other quarters."

A ranking suburban police official was more blunt. "Everybody lays this off on police, but the federal government has got to step in and close the {border} door," said Maj. James Ross, commander of investigative services for the Prince George's County Police Department. "They've got to get the Jamaica influx under control."