A secretary at Bethesda Naval Hospital returned to Cmdr. Donal M. Billig's court-martial yesterday to tearfully accuse the heart surgeon of lying under oath last week when he said he ordered records destroyed to save space.

The final day of testimony in the eight-week court-martial ended with the accusation by Sondra Getz, the former personal secretary to Billig, who had first testified last month about the destruction of the operating room records. The proceedings also included an unexpected examination of the preserved hearts of two of the five patients whose deaths prompted involuntary manslaughter charges against Billig.

A panel of nine officers, including a nurse and three doctors, will return today to the Navy Yard to hear final arguments in the case against the former head of cardiothoracic surgery at Bethesda.

Billig, 55, has been charged with five counts of involuntary manslaughter and 24 counts of dereliction of duty in connection with other operations he performed there in 1983 and 1984. His surgical techniques have been questioned during the trial as well as his eyesight, which is correctable to 20/400 in his right eye and hindered by poor depth perception.

Billig's former secretary, in her January testimony, said Billig told her to destroy his file of operating room notes on a day that he appeared to be upset, after a meeting with the executive officer at the hospital. She said she disagreed with the order, suggested it would "come to haunt us," but agreed to tear up the records that day. She described Billig as a "most honorable person" and someone who "never lied" to her.

Yesterday, Getz bowed her head and recanted her trust. "I completely believed Dr. Billig before," she said. "I don't now."

Getz said she asked to return to the witness stand after newspaper accounts indicated that Billig had testified that the records were thrown away to create filing space. "I was very, very upset," by the testimony, she said. "And I wanted to come here again because the truth is very important."

In a quavering voice, Getz disputed Billig's testimony, explaining that there wasn't a need for more file space. At least five drawers were empty then, she said. Two were on the floor -- and "one would have to be blind" not to see them, she said.

"Nobody will ever really know the truth of why he needed to do away with that file," she said in a choked voice to the hushed courtroom. "But Dr. Billig and I know that he is guilty of perjury." During the testimony, Billig sat with his eyes downcast.

Getz, questioned later by the defense, said she was uncertain when Billig told her to destroy the records. In January, she testified that Billig gave the order in late 1983 when he was the subject of an internal hospital investigation.

Yesterday, she said she agreed only "at the prosecution's persistence" that the event happened in 1983. She said she now believes it happened after August 1984.

Getz was one of six witnesses called by the prosecution to rebut defense testimony. Lt. Cmdr. Jonathan Lord, a doctor and consultant to the prosecution, also took the stand to discuss the condition of the hearts of the dead patients and offered two for examination.

Donning latex gloves, Lord picked up the preserved hearts of Lt. Col. Harold Coplan and Maj. William F. Grubb to explain the extent of disease in their aortas.

Other heart specimens supplied by the prosecution were examined. All were maintained, as part of a standard routine, after autopsies that were approved by relatives of the dead, according to Navy spokesmen.