Ropes of concertina wire stretch above chain-link fences, enclosing two aged structures on the grounds of St. Elizabeths Hospital. The buildings are named "Home" and "Relief," strange titles for a little-known federal detention camp in the District, the place where the "Freedom Flotilla" ended for dozens of Cubans.

Inside are "detainees" being held for a deportation that may never occur. President Carter welcomed them to the United States, but for the past six years they have lived behind barbed wire or in halfway houses, held in a legal and diplomatic limbo.

The federal government, through the Justice Department, will pay $10.2 million this year to private New York and Virginia firms to guard and care for the 142 mentally ill men who now live in the two St. Elizabeths buildings. Although they are situated in the middle of a federal mental hospital compound, the men behind the barbed wire have no contact with the rest of the hospital.

"It is an island we can't reach," said Ana Anders, director of a treatment program for mentally ill Hispanics just yards from the detention camp. "It's been here so many years, you can pass by it and ignore it."

Most of the men live in open dormitories that have hospital beds, lounges and classrooms. There are a few single rooms. Their treatment involves behavior modification and a token economy, in which points, which can be traded for telephone calls and items at a canteen, are awarded for good conduct.

The men isolated behind the fence were among the 125,000 Cubans who left the port of Mariel in 1980 and poured onto the shores of Florida after Carter pledged that the United States would "provide an open heart and open arms" to the refugees.

Among the 125,000 were a number of mental patients and criminals chosen by Fidel Castro to join the boat lift.

The "open arms" folded after five chaotic months in which government and civilian agencies struggled to cope with the flood of people. As a House of Representatives committee report stated, "What began as a gesture of compassion became a nightmare."

Riots broke out in temporary detention camps in Arkansas, Florida and Pennsylvania. Federal officials searched desperately, and unsuccessfully, for a governor who would accept another detention camp for mentally disturbed refugees, many of whom are thought to have been sent on the boat lift by Cuban authorities.

As cold weather approached and unrest grew, federal officials decided to use government property at St. Elizabeths and renovated abandoned buildings in 72 hours.

On Oct. 20, 1980, five days after 90 men and three women arrived in Washington, tensions erupted into a riot, quelled only when authorities handcuffed all the residents and tranquilized some of them involuntarily. Since then, the camp at St. Elizabeths has been relatively peaceful.

The number of Cubans detained at St. Elizabeths has fluctuated, as individuals are released into federal halfway houses but sometimes return. They, along with about 1,500 Cubans with criminal records who have been living in the old Atlanta penitentiary, "are social pariahs," said Tom Bourneman, the Public Health Service official in charge of Cuban and Haitian refugees.

U.S. immigration officials call them a variety of names: "entrants," "Mariel excludables," "undocumented aliens" and "deportees."

There is a similar indecision about their status. Because their mental problems or criminal records make them ineligible for entry into this country, the Immigration and Naturalization Service says they are simply being held until they can be deported.

In December 1984, the United States and Cuba agreed that 2,700 of the criminals and mentally ill refugees would be sent back to Cuba. But Castro angrily dismissed the agreement after the United States established Radio Marti and began broadcasting off Cuba's shores.

As a result, these Cubans are neither coming nor going. They are simply caught between two governments.

"They do not have status here," said INS spokesman Duke Austin. "They are aliens without status. The law says if you're mentally retarded or mentally defective, you are inadmissible to the United States."

Attorneys with the American Civil Liberties Union and other refugee assistance projects are troubled that "temporary" camps are in business six years after they were established.

"I do not understand why the INS has the legal authority to hold people indefinitely because they cannot be deported," said Gay Gelhorn, a D.C. attorney who counseled residents in the St. Elizabeths center last year before the deportation agreement collapsed. "There's a parallel with the Japanese war camps. The service should have to go to Congress and ask for permission for a new kind of facility."

But the INS has determined that this is unnecessary, Austin said, as the agency has won several lawsuits that uphold its right to detain excludable aliens. Robert Neptune, INS spokesman for the metropolitan region, added, "The law allows us to detain them as long as necessary." Gene Guerrero, director of the Georgia ACLU, disagreed. "These detention camps are being treated like they're an anteroom at Dulles and they're waiting for the next flight out."

Life inside the camp is much like other institutional life, according to federal officials, who would not permit a reporter inside, citing the residents' privacy.

But a Miami psychiatrist who worked at the St. Elizabeths center in the winter and spring of 1983 said the program had little in the way of psychotherapy but used extensive drug therapy. "There was very much use of prolixin injectables," said Dr. Josefina Khouri, referring to a tranquilizer. "They had social workers and psychiatric nurses who provided medication."

Khouri said the residents did not leave the hospital grounds during her three-month stay. But federal officials said there are field trips and said the residents play softball, swim and use an exercise yard. Bourneman said patients receive medication voluntarily. "Detention is not voluntary, but the treatment is," he said, adding that there are the usual internal reviews of the appropriateness of each medicine administered.

Documents released under the federal Freedom of Information Act show that the center, which at times has had as few as 25 residents, has a total of 86 guards on duty in three daily shifts. Guards are equipped with regulation riot gear, including face shield, riot baton and handcuffs. The cost for security, which is provided by Citywide Security Services of Brooklyn, N.Y., is $2.9 million this year. Another eight INS officials work at the center.

The guards do not carry guns inside the building but often have been seen carrying guns while escorting residents on the hospital grounds, according to several members of the St. Elizabeths staff, who said they object to the presence of guns and barbed wire in a mental health facility.

"If they are going to escort one of the detainees out of St. Elizabeths, they can be armed," explained Charles Troy, a contract specialist at the INS.

There are another 230 employes working there from Preventive Health Programs, a Falls Church firm that supplies doctors, social workers and other medical help to military hospitals, prisons and clinics across the country. The firm, which ran most of the government's first detention camps for the Mariel Cubans, recently signed its fourth contract with the federal government to continue operating the St. Elizabeths center. The three-year contract, which expires in 1988, is for $22 million.

"I don't see how it could be provided more cheaply, given the realities of INS policies," said Dr. Richard Cravens, director of the Refugee Mental Health Program at the National Institute of Mental Health. Added Bourneman, "The same people who criticize the spending of money don't want them in their communities," where care could be cheaper.

Austin, of the INS, said, "The assessment is that they are potentially dangerous. The criminal element from the Mariel boat lift is one of the toughest. It could be a combination of rape, pillage, plunder and burn . . . . Maybe the security is excessive, but we'd rather err on the side of caution." Dr. Ricardo Galbis, director of Andromeda, a D.C. nonprofit mental health clinic for Hispanics, said, "It's absurd. It's an extremely expensive program. No monies are spent in community support for Cubans in communities."

According to a recent report, since 1980 Andromeda has treated 393 Cubans living in the Washington area who arrived during the Mariel boat lift. More than half abuse drugs and alcohol, the treatment records show. More than one-quarter have attempted suicide. These same problems are seen at the center, Bourneman said. Several suicides have been attempted, but none was successful, he said.

Although in the early days detainees stayed longer, the federal government now estimates the average length of stay in the St. Elizabeths camp at 171 days per visit.

Residents are moved to one of eight INS-financed halfway houses across the country but often return to Washington for its greater security and intense treatment, Bourneman said. Jose Lasaga, a Miami psychologist who has worked extensively with Cubans from the boat lift, said geography is a barrier to treatment. "After having been psychotic in Cuba for years, those sent to the U.S. lost the best thing that would be able to help them: their support system of family and friends," he said.

Because of the uncertainty about the Cubans' fates, the Public Health Service workers are instructed not to discuss the residents' futures with them. Cravens said, "The men ask, 'What's going to happen to us?' We tell them not to focus on this."

Even the federal government's departure from the rest of St. Elizabeths, when the District government takes it over in October 1987, will not affect the camp's operation, federal and District officials said.

"The INS has set up the technicality that the property is equivalent to a boat in a harbor," said Ron Willis, staff member of the House District Committee. "It is separate and will continue under federal control."

Until the political situation between Cuba and the United States changes, federal officials said they are powerless to do anything but continue operating the camp.

But the result, according to Lucas Guttentag, an attorney with the Columbia University Immigration Law Clinic, is life behind barbed wire for men unfortunate enough to be caught up in the political stalemate. "The truth is that in America, indefinite detention has become a life sentence."