Created four years ago to usher in a new era of impartial justice, the U.S.-trained Haitian National Police force is grappling with allegations that its officers have been involved in a wave of murders, disappearances of detainees, drug-related crimes and other illegal activities.

After 20,000 troops, mostly Americans, dismantled a military dictatorship in 1994 and reinstated Haiti's first democratically elected president, the new police department was to be the cornerstone of justice reform. And even its harshest critics have welcomed the new force as an alternative to the repressive security forces that traumatized Haiti during the military government and the earlier dictatorships of Francois Duvalier and his son and successor, Jean-Claude.

But the implication of members of the new police force in human rights abuses and other illegal activities has focused concern on police lawlessness and raised questions about the department's ability to become an effective and credible force despite the sizable assistance provided by the United States and other countries.

"If you are asking me whether I am more concerned about rot in the police than a year ago, the answer is yes," said Colin Granderson, executive director of an international civilian mission here run by the Organization of American States and the United Nations. "We have both human rights concerns and concerns about the broader conduct of officers, specifically with respect to criminal activity, in particular drug smuggling."

A lot is at stake, not only for this Caribbean nation of 7 million people, the Western Hemisphere's poorest country, but also for the United States, which has spent about $75 million to help train and build the police force.

The alleged police transgressions have further eroded confidence in the department among the Haitian public, which already is widely distrustful of state security. "For me, I feel fear when I see their guns and their dark sunglasses. I want to trust them more and have freedom without worries that they will harm me. But there are too many bad stories," said Raymond Jean, 24, a Port-au-Prince shoeshine man.

From April through June alone, 50 killings, many of them summary executions, were attributed to police, compared to 31 for all of last year, according to Haitian and international investigators. Observers said the sharp increase in part reflects the heightened state of insecurity.

In a case that has drawn widespread attention, a number of officers under the command of Jean Coles Rameau, the Port-au-Prince police commissioner, are under investigation in the deaths of 11 detainees on the night of May 28 in the Carrefour-Feuilles neighborhood.

Seven officers have been arrested in connection with the slayings, including Rameau, who had fled to the neighboring Dominican Republic before he was apprehended and extradited. An eighth officer is at large after escaping from custody. The government has named a special three-judge panel to investigate the killings.

Allegations of police involvement in the drug trade have continued to surface in a country that has become a major transshipment point for cocaine and heroin bound for the United States from South America. Last week, four police officials were dismissed on suspicion of trafficking, a week after a half-dozen officers were arrested on charges of stealing hundreds of pounds of cocaine found on a boat docked in the northern city of Cap Haitien.

Investigators also have received information about plainclothes officers working with illegal vigilante groups that have recently reemerged in some communities, ostensibly in response to an increase in crime. According to a report last month by the international civilian mission, residents in the Port-au-Prince slum of Cite Soleil said 16 people were killed recently by one of the groups headed by police officers.

"Haiti has an authoritarian history, and it is easy to fall back into old practices," said Viles Alizar, coordinator of monitoring for the National Coalition for Haitian Rights. "We know the police are not an army, but they can act very much like one."

Although U.S. officials have expressed frustration over criminal behavior by officers, they said that in the case of human rights abuses the culprits appear to have been acting without official approval.

"The key is that there is no systematic violation of human rights," said U.S. Ambassador Timothy M. Carney, adding, "What is encouraging is that when there are abuses they move to address them."

The police department has been cited for good work -- including seizures of drugs headed for the United States -- despite its limitations; it has been hampered by inexperience and poor resources, ranging from inadequate manpower to a lack of basic equipment.

Officers also have to contend with the impunity enjoyed by many criminals at the hands of corrupt judges in a dysfunctional justice system. Officers are paid about $300 a month, a salary far above Haiti's annual per capita income of $250 but still considered very low.

The police department has dismissed more than 530 officers over the last four years for corruption, abuse of power and other disciplinary infractions. Of that total, 54 are awaiting trial. Because the officers were removed, the size of the force has decreased just as it is facing a surge in crime and violence stemming in part from political instability. The department is scrambling to devise a security plan for upcoming parliamentary elections.

Officials said the number of police officers has dropped from a high of more than 6,500 about 20 months ago to roughly 6,000 today, although police personnel and international observers say the figure is probably lower. "I am concerned about the numbers." said Robert Manuel, secretary of state for public security. "We have to train even more officers, but we do not have the resources."

Officials say it is doubtful that the police force will be able to reach its goal of between 9,500 and 10,000 officers by 2003. "Our view is that they are not doing enough to maintain, let alone build," said Gary Bennett, manager of the U.S. Justice Department police training program in Haiti. "We are at the hardest point of development."

Officers say their jobs have been made more dangerous by the 300 or so Haitian criminals deported each year from the United States and elsewhere and because the United States failed to disarm state security forces after reinstating president Jean-Bertrand Aristide in 1994. Since the force's first officers were deployed, 59 have been killed.

Manuel and Police Chief Pierre Denize have been the targets of a public campaign -- attributed to members of Fanmi Lavalas, the party headed by Aristide -- that has been described as an effort to destabilize and politicize the police to pave the way for Aristide's return to the presidency.

Aristide, who spent three years in exile in the United States after he was ousted in a military coup in 1992, remains popular among the country's poor and is heavily favored to win next year's presidential election. Fanmi Lavalas has denied any involvement in the campaign against the police.