If America wants to treat presidential assailant John Hinckley rather than punish him, he has been sent to the right place. In the wards for the criminally insane at St. Elizabeths Hospital, Hinckley and other patients receive some of the most intensive psychiatric care available in any public institution, at a cost of $66,000 a year each.

The Howard Pavilion, where Hinckley is being kept, has a national reputation for excellence. It has a staff-patient ratio of better than one-to-one, including a score of full-time psychiatrists and psychologists, 192 "forensic psychiatric technicians" encouraged to behave more like nurses than guards, and assorted doctors, social workers and therapeutic specialists.

The pavilion's 239 patients choose from a wide range of educational, recreational and vocational therapeutic activities, from mock businessmen's lunches to "sock hops" with patients from men's and women's wards, to a course in street law.

Hospital officials say the various programs have been so successful that the average patient--whether originally charged with a felony or misdemeanor--is allowed to walk unescorted across the open campus to an "industrial therapy" job within a year of arrival.

"It's difficult to evaluate whether you have clinical improvement if you never take the chain off their neck," said Joseph Henneberry, 57, a registered nurse who is director of the pavilion, but he emphasizes that new freedoms are granted only after careful deliberation.

In interviews with a dozen key staff members during a tour of three of the Howard Pavilion's 12 wards--the first press tour since Hinckley was sent there June 22--a picture emerged of a staff of professionals working with patients, many of whom have committed violent acts, in an effort to control their psychoses through drugs and therapy and return them to normal community living.

"We are able to improve their ability to handle work and social situations," said Dr. William H. Dobbs, superintendent of St. Elizabeths. "It seems unlikely that we can do anything curative. We are able to effect a good remission . . . . The problem is possible relapse under stress."

Hinckley is being kept in a "pretrial" ward even though he was found not guilty by reason of insanity ("NGI" in hospital parlance) in the attempted assassination of President Reagan. Here he is being studied closely by a psychiatric team that will advise the U.S. District Court before Aug. 2 on whether he still is mentally ill and, if so, whether he is likely to be dangerous to himself or others if released.

Under the law the court then has 10 days to hold a hearing on whether Hinckley should be released, unless Hinckley waives the requirement. Henneberry said that in 15 years of working with the criminally insane at St. Elizabeths he recalls only two cases in which patients were released after such a preliminary hearing. In almost all cases, he said, they are committed by the judge for treatment until their mental illnesses can be controlled or put into remission.

In preparation for this hearing, Hinckley is being studied by a team of psychiatrists and other specialists; he is receiving a full battery of psychological tests and is participating in lengthly interviews. He is watched carefully 24 hours a day, even when he is in his private room. For the first two weeks, the nursing staff wrote three reports on him daily.

The Howard Pavilion building itself is large -- five stories including a wood-paneled gymnasium where visiting college basketball teams play the patients and an auditorium where bands and musical groups provide entertainment. Of the 12 wards, nine are maximum security, one medium and two minimum. The wards have an institutional look with polished linoleum floors. They are spotlessly clean, with small individual rooms and small open-bay areas with the beds separated by high dividers. Each ward has a nursing station for the staff and a day room with a pool table or table tennis and a color television set.

"You have a right to privacy and dignity," say signs on the walls of each ward."You have a right to treatment regardless of race, religion, sex, culture, age or handicap."

Esther Moore, a registered nurse now assigned to Ward 9 where Hinckley is being studied and treated, said that in the past decade there has been an increasing emphasis on therapy. "The employes are more therapy-oriented than prison-oriented, more willing to have therapy groups, to counsel the patients . . . . We're thinking in terms of getting them better."

The regular daily therapeutic programs available to patients are educational, vocational, recreational, religious and "industrial"--this last being a supervised job on the hospital grounds. Patients interact constantly with psychiatrists and psychologists. There are social workers to help them maintain contact with friends and families. Patients participate in role-playing groups, "hostility groups" where they are supposed to become less hostile by articulating their rage, and "mental competency groups" where they are taught the legal meaning of mental competency.

The objective of the program of drugs and therapy, according to Dobbs, is not to cure patients -- this is considered beyond the reach of present knowledge about mental illness -- but to control the illnesses and put them into remission so the patients can return to normal community living. Many of them are required to continue to take psychotropic drugs once they are back home -- drugs that help control their mental state.

Officials would not allow Hinckley to be interviewed nor his ward visited, but they took a reporter to a similar "pretrial" ward where other inmates are being evaluated. In these wards, about 400 inmates pass through annually as they are studied for 30- or 60-day periods. Well over half of these are found mentally competent to stand trial.

Although the Howard Pavilion receives relatively few NGIs--only 18 last year--roughly four-fifths of the pavilion's patients live in the "posttrial" wards since the NGIs typically stay in the program for several years and some for decades. It is one of these wards where Hinckley will probably be transferred after his hearing or its waiver in early August.

An outside observer can sense immediately a difference between the pretrial and posttrial wards. Inmates in the pretrial wards are noisier and less disciplined, perhaps because, the psychiatrists suggested, most of these inmates are not being given tranquilizers or other psychotropic drugs during the period they are being studied, while more than 90 percent of the patients on the posttrial wards receive large doses of medication. Also, most of the pretrial inmates are not found to have serious mental problems and many resent being sent there.

"Here are the quacks!" shouted an inmate when Henneberry and other hospital officials escorted a reporter into pretrial Ward 8. "What you doing up here, quack?" The inmate was playing a lively game of cards with three other inmates at a table in the day room. Other inmates in the room were watching television or simply sitting in chairs. No aberrant behavior was apparent.

In Ward 12, a posttrial ward for NGIs, the inmates appeared completely normal. They were reading, talking to one another and to staff members, watching television. There were no taunts; instead, they seemed to appraise the visiting entourage carefully and quickly, greeting them with smiles and pleasantries.

The ward administrator, psychologist Morgan Jones, said some of the patients have "explosive and volatile tempers," making ward life "an explosive situation. It doesn't take much. We try to stop this by being creative. It's such a confining, limiting setting. We try for a less tense and more free atmosphere."

One way this is accomplished is through a number of programs devised by the staff -- including the "businessman's lunch," sock hop and a law course.

Dr. Joseph Smith, a staff psychiatrist, said he got the idea for the mock businessmen's lunch one day when he saw a patient spiffily dressed in a blue suit and white shirt. "I got to thinking about that," he said. " . . . We had a businessmen's lunch. We had 150 people from the community and the hospital. Everyone dressed formally. Our patients looked so good those who didn't know them couldn't tell who they were. Our accreditation team here couldn't tell."

Smith said that at the "sock hop" the records were scratchy so a nurse got the idea of placing four radios in the corners of the day room and tuning them all to the same station, thus achieving a stereophonic effect. "They had a great time," he said.

Smith said a street law class, covering such subjects as landlord-tenant relations, was taught by Georgetown University Law School students. "If they had psychoses and delusions you didn't see that in this class," Smith said. "They were apparently able to put those aside."

In other classes, Smith said, he would "pick a word apart," discussing with patients the meanings of words like freedom and responsibility. "Somebody said, 'Will you teach us what hallucinations are?' After 15 minutes they . . . talked about their own hallucinations, which they hadn't talked about before."

E.L. Tyler, a forensic psychiatric technician, described an afternoon soap opera program she planned to begin for patients, allowing the patients to produce their own dramatic soap operas. She has posted a notice on the ward bulletin board, which says, "COMING SOON! SOAP DRAMA GROUP." Many of the ward's 29 patients have signed up.

Ultimately, when a treatment team and other officials think a patient is ready, he or she may be given the freedom to walk to a job somewhere on the large hospital campus or to spend a few hours alone at the hospital canteen--the risks that Henneberry said are necessary in the treatment process.

"We do this on a very slow, careful basis, as carefully as we know how," said psychologist David Powell, a top administrator at John Howard. "If we have somebody who looks bad, and we think he can have privileges and the individual maintains it well, that's a success. To the outside community that looks like, 'My God!' "

There is a price for taking such chances, the officials said. While there have been only two escapes from the pavilion's locked wards in the past decade, 77 criminally insane patients since 1959 have walked off and never returned after being granted therapeutic freedoms. Nine of those walkaways took place last year.

Henneberry said that in some cases the walkaways are relatively stable people who simply go home to their families and get jobs.

"One guy was doing so well, when he was returned to the pavilion we had letters and phone calls galore about him. His employer said, 'We guarantee his job back.' "

Henneberry said he thinks the public, while leery about what goes on in the pavilion, would be surprised by the truth of it. "People generally expect bars and padded walls, but it's not like that."