A heart surgeon who supervised operations performed by Cmdr. Donal M. Billig, a former surgeon charged in connection with the deaths of four patients at Bethesda Naval Hospital, described Billig's surgical techniques yesterday as "too rough" and said Billig "sacrificed accuracy for speed."

"I was constantly on my guard when I operated with him," said Dr. Reginald Peniston, now head of the cardiothoracic unit at Howard University Hospital. "And I recommended that perhaps . . . he should search his soul about whether he wanted to continue."

Peniston's statements, made in a preliminary hearing at the Washington Navy Yard, constituted the first public testimony in the investigation of Billig, who was charged by the Navy earlier this year with four counts of involuntary manslaughter and 24 counts of dereliction of duty in connection with other operations he performed.

Billig, 54, operated at Bethesda from January 1983 through November 1984 and was referred for general court-martial in June after internal investigations by the Navy raised questions about his competence. Those inquiries resulted in 10 other Naval officers receiving sanctions for their part in the hiring and approval of Billig and revealed that he is legally blind in his right eye.

The hearing yesterday was part of a pretrial investigation that will lead to the court-martial, the most serious of military prosecutions, expected to begin in October. Peniston, 37, is the first of about 10 witnesses expected to testify this month.

Responding to questions from prosecutors and defense attorneys, he spoke for more than two hours yesterday about his relationship with Billig, who became head of the Bethesda cardiothoracic department in June 1983 after Peniston retired from the service.

Peniston described Billig, a 1957 graduate of the University of Louisville Medical School and a protege of famed heart surgeon Dr. Michael DeBakey, as someone who "certainly in terms of previous experience . . . was a valuable asset and had seen a lot."

When Billig performed chest operations, he was "very facile and he appeared to perform very well under certain situations," Peniston said. But in Peniston's area of expertise -- heart surgery -- Billig was not a person to be trusted, Peniston said.

Peniston operated twice with Billig before March 1, 1983, when a triple bypass operation was scheduled for Harold Coplan, a retired Air Force lieutenant from Gaithersburg.

After that failed operation, when stitch after stitch inexplicably broke from the heart vessel that they were trying to repair, Peniston said, he realized that Billig "did not have the expertise in the operating room that he had in other areas."

"I look back at that operation and I knew it could have been done better," Peniston said. "And I remember his words very well [when problems began occurring]: 'Don't worry, I've done this many, many times before.'

"At the end of the day, I was in absolute shock that we lost that patient," said Peniston, who estimated the risk of death in that case as 1 percent.

Denver Graham, one of three attorneys representing Billig, questioned Peniston thoroughly about his role in supervising the doctor. Peniston said Billig had been appointed to Bethesda as a heart and chest surgeon although he had not practiced heart surgery for five to six years.

Billig had agreed to be retrained for six months to sharpen his skills, and Peniston was one of the doctors who had to supervise him.

Peniston, who was acting head of heart and chest surgery from March through May 1983, said he was responsible for Billig during the failed operation. But Billig's extensive background and apparent seniority in the specialty of heart surgery had led Peniston to believe that Billig would have few problems in the operating room.

"I decided to change my approach," Peniston said about the days following the Coplan operation. "I relied then on my own opinion when I operated with him. I have never been so exhausted in operating to make certain there was no more rough handling of tissue."