It is billed as the court-martial of a heart surgeon at Bethesda Naval Hospital. Yet the trial of Cmdr. Donal M. Billig, only the second Navy doctor ever accused of killing a patient through culpable negligence, may shine a rare and harsh light on the breakdown of a military medical system that serves 10.2 million Americans.

Beginning today, a panel of Navy officers, including three doctors and one nurse, will hear an estimated 75 witnesses -- civilian and military doctors, nurses, patients and representatives from each branch of the armed forces -- recount operations, frustrations and fears stemming from what the government is now calling a case of "much wrongdoing by Navy doctors, one of which is the accused." The court-martial at the Washington Navy Yard is expected to last eight weeks.

A year after the disclosure of unprecedented internal reviews of medical practices and problems in all branches of the armed forces, the testimony can be expected to pique the interest of anyone who has used a military hospital, from the lowest of the enlisted to the highest in elected office.

The medical staff at Bethesda, the Navy's premier hospital and the institution where President Reagan receives treatment, has been uncomfortably aware of the case that targets the hospital's former chief of heart surgery.

Eight other officers, including two men who once held the highest positions at the hospital, have received sanctions for their roles in appointing and approving Billig. One recruiter, Cmdr. Reginald Newman, is before a court-martial on charges that arose from the Billig investigation. The officer who originally recruited Billig in Pittsburgh in 1982, Lt. Cmdr. Jerry Penn, also has been charged.

National concerns, too, play a role in making the case one to be reckoned with. The federal government, not individual doctors, is liable for medical mishaps in military hospitals. Since Billig was charged in June, families of the dead and other patients treated by Billig have filed 15 claims against the government. In a year of federal budgetary woes, they are requesting a total of $75.7 million in compensation, according to Navy spokesmen.

Billig, 54, has been charged with the involuntary manslaughter of five patients at Bethesda and 24 counts of dereliction of duty in connection with heart operations that he conducted in 1983. A cum laude graduate of the University of Louisville Medical School and former protege of renowned surgeon Michael DeBakey, Billig joined the Navy after 20 years of academic and private practice and has defended his service as having been conducted "in the highest traditions of medicine."

The jury, a panel of eight Navy captains and one rear admiral, will have to be convinced beyond a reasonable doubt that the doctor killed his patients -- four retired servicemen and the wife of a retired serviceman -- through "gross, wanton and reckless disregard" of surgical standards. As in a civilian court, the panel will listen to testimony from witnesses and be instructed by a judge, in this case, Air Force Capt. Philip Roberts from San Francisco.

But unlike a civilian jury, which requires a unanimous vote to convict, a vote of only two-thirds of the panel's members is sufficient for conviction. If the panel fails to get that two-thirds vote, Billig is free -- unlike in a civilian court, where a mistrial would be called.

At issue in his trial are Billig's surgical techniques, his physical abilities and the life-and-death decisions he had to make in the operating room.

Public documents and statements have revealed that Billig applied to the Navy four years after he suffered a tennis injury to his right eye. Despite numerous operations seeking to correct the problem, the injury caused folds and scars to develop over the retina. According to a Navy examination conducted in the midst of the investigation over his competence, the doctor has a lack of depth perception and poor eye-hand coordination and has 20/400 vision in his right eye. Doctors say this means that he legally is blind in that eye.

The general court-martial, the most serious of military proceedings, is open to the public and is expected to provide a clearer picture of what the Navy knew when it accepted Billig for a commission in 1982, and with whom he discussed his physical limitations when he was appointed to Bethesda.

From a list of 53 witnesses presented by the prosecution last week, Billig's colleagues are expected to be questioned. They include his former commanding officer, Commodore James Quinn, and executive officer, Capt. Leon Georges, who received letters of censure for their role in appointing Billig and have retired.

Billig was commissioned in December 1982 and appointed to Bethesda as a heart surgeon in January 1983. He had not practiced heart surgery for six years but, pretrial testimony and interviews have shown, he underwent a retraining program at Bethesda designed to allow him to undertake major and complicated heart procedures.

Before the year's end, Billig received approval to undertake those kinds of procedures and to be named head of the hospital's cardiothoracic department. That approval came, according to the prosecution, despite repeated complaints by Navy doctors about his techniques, despite warnings from Army doctors who assisted him, and despite concern expressed when Bethesda officials were told that Billig once lost his operating privileges at Monmouth Medical Center in New Jersey after charges that he lacked surgical competence.

Prosecution attorneys said last week that they will present witnesses, including one from the New England Medical Center in Boston, who will say that Billig's professional problems reach back 15 years. His last years of private practice in Pittsburgh, where he worked before joining the Navy, ended in a harsh assessment by cardiovascular surgeons in that city, the prosecution has argued in court.

Defense attorneys contend that those accusations are based on professional jealousies, an argument that Billig used in 1981 when he unsuccessfully fought a challenge to his competence leveled by Monmouth officials. The argument in that case, outlined in court files in Freehold, N.J., questions the competence of the other surgeons with whom Billig practiced and cites experts who defended Billig's techniques as acceptable standards of practice.

In pretrial investigations, Billig's defense lawyers have argued strenuously that his techniques at Bethesda were good procedures that failed at times only because of the degree of disease in the hearts he was trying to save.

The trial is a battle between two groups of military lawyers, with the defense being assisted by civilian attorney Denver Graham and the prosecution adding a Navy doctor for expertise. Graham has said that he has no significant criminal trial expertise, but he has had a career based on malpractice law. He will be defending Billig on the involuntary manslaughter charges.

Billig's two Navy lawyers will be handling the 24 counts of dereliction of duty, striving to demonstrate that Billig operated with the full knowledge and authority of his superiors at Bethesda.

In preparing for the trial, the sides have produced thousands of pages of potential evidence.

Evidence approved by the judge last week and scheduled for viewing today will include preserved human hearts. Although not the hearts of the five persons in whose deaths Billig is charged, they will be specimens from heart patients. The prosecution said last week that the panel of officers deciding the case, which includes three doctors and one nurse, will be asked to examine and feel the specimens.

If convicted on all counts, Billig could be dismissed from the Navy, lose all pay and allowances and be sentenced to a maximum of 21 years in prison.