A secretary at Bethesda Naval Hospital testified yesterday that Cmdr. Donal M. Billig told her sometime in the fall of 1983 to destroy his file of operating room notes and not to keep such records in the future, an order she disagreed with and said "would come to haunt us."

Sondra Getz, Billig's personal secretary in the cardiothoracic unit at Bethesda, said she tore up the records that day and put them in office trash cans. "I don't think we should do it," Getz said she told Billig, who is charged with involuntary manslaughter in the deaths of five patients at the hospital. "But I'll do what you tell me to."

Getz's testimony, heard during the court-martial of Billig at the Washington Navy Yard, came the same day that a Navy officer who helped recruit the doctor was found guilty by another court-martial panel of lying to investigators.

Cmdr. Reginald E. Newman, who recruited Billig in 1982, was convicted of two counts of making false official statements, one count of dereliction of duty and two counts of perjury. The decision followed 2 1/2 days of deliberations by the court-martial panel, convened at Bolling Air Force Base, and two weeks of testimony.

Newman, 53, faces sentencing today by the same panel that found him guilty. The maximum sentence the 35-year Navy veteran could receive is 21 1/2 years in prison, dismissal from the service and forfeiture of pay and allowances.

Newman's trial ended as Bethesda personnel who worked with Billig in 1983 and 1984 testified about how investigations into the heart surgeon's surgical competence were handled during those years. In addition to the involuntary manslaughter charges in five deaths in 1983 and 1984, Billig, 54, has been charged with dereliction of duty in connection with a dozen other operations he did without supervision in 1983.

Getz, who still works at Bethesda, said she was told to destroy reports, maintained in Billig's office, on a day that Billig appeared to be upset.

He looked "completely out of character," she said. "Upset . . . it looked like the fight was out of him." She said she believed Billig had just left a meeting with then-Executive Officer Leon Hodges when he met her in the reception office of the hospital.

Hodges testified last week that he found out during a meeting with Billig in October 1983 that the heart surgeon's competence had been criticized by a New Jersey hospital in 1980 and that the doctor had been asked to leave. Hodges said that in light of that information he ordered Billig not to perform any heart operations and asked for an investigation into Billig's credentials. Billig was cleared after that one-month investigation.

Getz indicated yesterday she was surprised by the request from Billig, who she described as a "most honorable person . . . a very good administrator" and someone who "never lied" to her.

"I said 'What?' " Getz said when Billig first told her to get rid of the records that detailed operations from beginning to end. "He repeated that we shouldn't keep any more records and that we should get rid of the ones we had . . . . I said I thought it wasn't a good move . . . that I thought it was something that would come to haunt us."

Getz said yesterday she "had the impression that somebody had told Dr. Billig not to keep the records anymore."

Getz said Billig told her months later, in February or March 1984, that she could resume maintaining records of operating room notes, and she did.

Beginning the second week of testimony in the court-martial, the prosecution also introduced the first witness to question the competence of Billig in connection with the five patient deaths. Cmdr. Bruce Lloyd, chief of cardiology at Bethesda, said yesterday Billig's actions during the operation of retired Naval Petty Officer Joe B. Estep, 66, of Temple Hills could be linked to the man's death five days later.