An Alexandria Circuit Court judge yesterday found a Northern Virginia man who had a history of mental illness guilty of murder in the death of a Dale City waitress whose partially clothed body was discovered in a closet at the Southern Towers apartment complex.

Judge Donald H. Kent's verdict came after hearing what he called "overwhelming evidence" that Thomas M. Mullens was not insane at the time of the April 30, 1981, strangulation murder of Phong Campbell. Mullens had pleaded not guilty by reason of insanity.

Shortly after the woman's death, prosecutors said Mullens took a taxi to St. Anthony's Catholic Church, 3305 Glen Carlyn Rd., where he told a priest, the Rev. Eugene Schnipke, of the murder. Schnipke testified that Mullens admitted killing the woman.

Mullens' attorney, Nolan B. Dawkins, argued that his client was insane at the time, but two people who examined Mullens disagreed.

Alan McFarland, a Fairfax County psychologist who had treated Mullens for a number of personality disorders including schizophrenia, told Kent that he could not be certain that Mullens, 21, was mentally ill when he wrapped a belt around the 28-year-old woman's throat and choked her to death.

That opinion was shared by Henry Gwaltney Jr., a clinical psychologist at Central State Hospital in Petersburg where Mullen was sent for observation. "There was no indication that on that day he was experiencing any disorder that could give raise to insanity," Gwaltney testified.

According to testimony, the woman's death occurred shortly after Mullens returned to the Washington area from a brief Army stint in West Germany. At the time he was often confused, drifted and drank heavily, witnesses said.

On April 30, the day after he made an appointment to see a psychologist, he went to Valle's Restaurant in Springfield and talked with Campbell, a Prince William County resident and a friend and coworker of his mother.

According to police, Campbell accompanied Mullens to his apartment complex at 4901 Seminary Rd. She told friends she was going with Mullens to help him move his clothes to another location where he was planning to move.

Mullens maintained that he didn't remember what happened in the apartment. He told doctors at Central State that he remembered only "going into the closet and seeing dark spots and hearing a woman scream," according to Gwaltney.

Police said they found Campbell's partially clothed body in Mullens' closet with a necktie stuffed in her mouth and shaving cream smeared over her face.

Sentencing was set for for June 14.