A Navy officer was acquitted yesterday of charges that he lied to investigators about his part in recruiting Cmdr. Donal M. Billig, a Bethesda Naval Hospital surgeon convicted last month of involuntary manslaughter and negligent homicide in the deaths of three patients.

Lt. Cmdr. Jerry D. Penn, 42, had been charged with perjury and conduct unbecoming an officer in connection with testimony he gave before a Navy investigative board in April. His acquittal yesterday by a military judge, Marine Corps Lt. Col. Hugh S. Atkins, followed a week of testimony in a court-martial at the Navy Yard in Washington.

Atkins announced his decision after hearing closing arguments yesterday and deliberating several hours. Penn, who processed Billig's Navy application in Pittsburgh in 1982, had chosen to have the case heard by a single military judge rather than a panel of Navy officers.

Penn's acquittal marks the close of a number of sanctions stemming from a yearlong investigation into Billig's record and the quality of medical service at Navy facilities.

Billig, 55, is serving a four-year prison term at Fort Leavenworth, Kan., and eight other officers have been disciplined in the case.

The charges against Penn were related to his testimony before an investigative board. The Navy alleged that Penn lied when he told the board that he had received and forwarded a letter of reference for Billig from the Monmouth Medical Center in New Jersey, where Billig had practiced previously.

"The acquittal shows the government just failed to prove beyond a reasonable doubt in [the judge's] mind that Lt. Cmdr. Penn had lied," said his attorney, Lt. Lewis Lang.

Lang said Penn, who is assigned to Naval Medical Command headquarters in Washington, would not comment on his acquittal. Navy officials also declined to comment.

Another recruiter, Cmdr. Reginald E. Newman, was convicted of two counts of perjury concerning the circumstances of Billig's recruitment. He was fined $10,000 and ordered to forfeit $2,000 a month for 10 years if he stayed in the Navy.

Penn testified under a grant of immunity at Newman's and Billig's trials, saying he had told his superiors about Billig's professional problems at the New Jersey hospital. Several charges against Penn were dropped before testimony began last week.