Susan S. Rooney, 20, whose mother was found strangled and who alleges in a civil lawsuit that her stepfather, Dr. David K. Davoudlarian, did the killing, testified in court yesterday that her mother wanted to leave Davoudlarian but was "afraid he might do something" to her if she did.

Rooney is the older of two daughters of Susan Davoudlarian, 40, whose body was found in a car parked in the long-term lot at Dulles International Airport on June 12, 1983.

No one has been charged in the woman's death, but her daughters from a previous marriage and her estate have filed civil lawsuits alleging that Davoudlarian, a Northern Virginia gynecologist, killed her. Davoudlarian has denied in sworn depositions any knowledge of who killed his wife.

Rooney, testifying in the Fairfax County Circuit Court trial of the suit filed by the estate, which seeks $10 million in damages, said her mother's marriage to Davoudlarian, 49, was acrimonious.

The daughters' suit, which will follow the current case, seeks to prevent Davoudlarian from collecting $750,000 in life insurance and property.

She told the jury and a packed courtroom that her mother had several times told her she wanted a divorce, but Davoudlarian refused to even discuss it.

"I said to her, 'Well, why don't you just leave,' " Rooney testified, "and she said, 'I can't do that, I'm afraid he's going to do something to me.' " "Like what?" Rooney said she asked; she said her mother replied: " 'I don't know, just that he might do something.' "

Rooney also testified that her stepfather asked her boyfriend not to spend the night at the Davoudlarian home in Annandale the night her mother disappeared. Police have said they believe Susan Davoudlarian was killed at home.

Rooney's friend had frequently spent the night on a downstairs couch, according to depositions in the case. She testified that her stepfather's request struck her as unusual because it was he who had first suggested the arrangement, since the boyfriend lived in the District.

Another witness yesterday was Susan Davoudlarian's father, Marlin Stewart, who discovered his daughter's badly decomposed body eight days after she disappeared. He provided the trial's most dramatic moment so far when he described his first close look at the body.

"They already had the body in the body bag, and they asked me to ID it, and I couldn't really," Stewart said, his eyes filling with tears and his voice faltering. Unable to continue, he dropped his head to the witness stand and began to sob quietly.

Judge Lewis H. Griffith called a recess to permit Stewart to regain his composure.