Nine Navy officers, after listening to five hours of conflicting legal arguments that portrayed Cmdr. Donal M. Billig first as a clumsy egocentric and then as a hard-working specialist, began deliberations yesterday in the heart surgeon's court-martial.

Billig, 55, the former chief of cardiothoracic surgery at Bethesda Naval Hospital, is charged with involuntary manslaughter based on the deaths of five persons he operated on at the hospital in 1983 and 1984. He also faces 24 counts of dereliction of duty for operations he performed unsupervised in 1983.

The officers deliberated for more than three hours before adjourning for the day.

If found guilty of all charges, Billig could be sentenced to 21 years in prison, dismissed from the Navy and fined. According to instructions given to the military jury yesterday, Billig also can be found guilty of related but lesser charges that carry lighter penalties. For instance, in four of the patient deaths, Billig is also liable to charges of negligent homicide or dereliction of duty.

Yesterday's final arguments by the defense and the prosecution capped an eight-week court-martial that followed a year of study by the Navy of the competence of Billig, who was commissioned in December 1982. Since an initial inquiry began in 1985, the same year of critical press reports and congressional scrutiny of military medicine, nine other Naval officers have received sanctions for their part in the Billig case.

Both the prosecution and the defense took care yesterday to note the serious consequences of a conviction in the trial, which brought 60 witnesses to the stand. It is the result of the Navy's second such manslaughter charge ever lodged against a military doctor.

"This court-martial is regrettable in the sense that it will cause irreparable damage to the reputation of a hard-working surgeon," said the defense attorney, Lt. Cmdr. Stephen Baker, adding that a wrong decision could "brand Dr. Billig a killer for life."

Col. Gerald Miller, the chief prosecutor, outlined alleged mistakes that he said occurred during the five operations in which patients died and said they revealed a "pattern" that was an indictment of the heart surgeon's abilities and honesty.

"The accused's approach to the charges appears to blame others when possible . . . never admit his own errors and not to learn from past mistakes," Miller said.

Miller, with little emotion and a methodical manner, told the Navy jury that evidence had shown that Billig had a serious vision problem and used outdated surgical techniques to perform delicate operations such as those undertaken on the five patients who died: retired Lt. Col. Harold Coplan of Gaithersburg, retired Petty Officer Joe Estep of Temple Hills, Md., retired Maj. William Frank Grubb Jr. of Lancaster, S.C., retired Lt. Col. John Kas Jr. of Cape Cod, Mass., and Lois Parent, wife of Marine Sgt. Maurice Parent of Havelock, N.C.

Miller, citing medical reports that showed Billig had poor depth perception, offered specific examples when he said the surgeon was negligent to his patients. In the Parent case, Miller said, Billig "clumsily tore her aorta and ended her life . . . . The standard of care was clearly violated by this arrogant, egocentric, clumsy surgeon."

In the case of Kas, an operation that left the patient's chest so swollen that it could not be closed, Miller said Billig left his patient to the care of nurses and residents in the intensive care unit.

For two hours, Billig could not be found while Kas was "bleeding over his chest, over his shoulders and on the floor." The patient died a few minutes after Billig returned to the scene, dressed in his Navy blues and holding a coat, Miller said.

Miller also said that Billig knew he should not operate alone until September 1983 and he lied about past professional problems to get those privileges.

Billig's defense counsel Baker said it was evident from testimony that no one, including Billig, understood his staff status at Bethesda from June through September 1983.

"The people who were involved in those decisions don't really agree as to what happened," Baker said. "And they are all adamant in their recollections."

In a clear, persuasive manner, Baker detailed conflicting testimony from former Naval officers who supervised Billig during that time. Paper work that should have convincingly outlined whether Billig had the privileges is not clear, Baker said.

"We know from the testimony that 1983 was not a banner paper work year at Bethesda Naval Hospital . . . . The practice there was to do things verbally with paper work to follow."

Baker urged the panel to believe testimony given by his client over five days and then asked them to also consider that Billig was being made a scapegoat for a range of surgical errors.

"He used acceptable techniques in the face of known complications and other surgeons would have acted similarly," Baker said.