Defense lawyers for Wayne B. Williams brought in the chief pathologist of the Israeli army today to testify that he found no evidence of murder in autopsy reports on the two black men Williams is charged with killing.

The defense also produced a young black woman who told the jury that she has had sex with Williams and is his girlfriend, an apparent effort to refute prosecution testimony suggesting that Williams is a homosexual.

Dr. Maurice Rogev, chief of the medical-legal bureau of the Israeli army, said he has "a feeling" that Nathaniel Cater, 27, died from a condition related to his enlarged heart. He said Jimmy Ray Payne, 21, "possibly may have drowned," but cautioned that he could not reach any definite conclusions about the cause of either death.

Rogev, educated in South Africa, Great Britain and the United States, was a government pathologist in Kenya for 17 years, and was the personal physician to Kenya's late president, Jomo Kenyatta. He said he has worked for Scotland Yard and was sent to Uganda in 1979 to recover the body of Dora Bloch, a hostage who was killed during the Israeli raid on Entebbe Airport in July, 1976.

Rogev implied that the Fulton County medical examiner's office should have performed more laboratory tests on the two bodies before stating any conclusions about their deaths.

Payne's body, clad only in red undershorts, was found floating in the Chattahoochee River on April 27, 1981, five days after he was last seen alive. His death was ruled an asphyxiation.

On May 24, Cater's nude body was found less than 100 yards from the site where Payne's body had been recovered. The medical examiner said he died of strangulation. A prosecution witness has testified that Cater was last seen alive on May 21, holding hands with Williams outside a movie theater in downtown Atlanta.

Gwendolyn Harden, a young woman who said she had known Williams for 11 years, testified today that she had gone to movies with him, kissed him, had sex with him and considers herself his girlfriend. She told defense attorney Alvin Binder that she is not ashamed of being Williams' girlfriend.

Under cross-examination by the prosecution, Harden said she would not deny that she told an FBI agent last summer that she believed Williams did not have a girlfriend. She said, however, that she did not remember saying that to the agent.

Harden admitted under cross-examination that she had not been to visit Williams in jail, where he is being held during his trial, but she said that was because his parents didn't want her to.

Williams is charged only with murdering Cater and Payne, but prosecutors have been allowed to introduce evidence from the cases of 10 other young Atlanta blacks who died between July, 1979 and May, 1981.

Robert Henley, who shared a room with Cater at a downtown transient hotel for 2 1/2 months before his death, testified for the defense today that he last saw him alive on the morning of May 19, the day before Cater's 28th birthday.

Under cross-examination, he confirmed that Cater knew Bobby Henry, the witness who testified that he saw Cater and Williams holding hands on May 21.

Asked later by defense attorney Mary Welcome if he knew whether Henry is reliable or unreliable, Henley replied, "I guess reliable."

Anthony Cater, Nathaniel Cater's younger brother, testified today that he last talked to his brother on May 18, 1981, and expected him to visit their father's apartment on May 20.

He said that their father usually gave Nathaniel money on his birthday, and that Nathaniel had never failed to visit on his birthday unless he was in jail. But Nathaniel did not visit on May 20, he said.

The defense has tried to establish that Cater was killed before 3 a.m. on May 22, when police say they believe that Williams threw Cater's body into the Chattahoochee River from a bridge.