LOS ANGELES (AP) _ O.J. Simpson quarreled with his estranged wife over sex, and once parked around the corner from her house late at night and stood outside, seemingly trying to peer in, two of her former next-door neighbors testified Friday.

The testimony, offered in an effort by prosecutors to depict Simpson as a jealous, obsessed man who stalked his wife after she had moved out, set the stage for Nicole Brown Simpson's sister, Denise Brown, to testify about the couple's turbulent relationship.

Carl Colby, a former neighbor of Ms. Simpson's, testified that he called 911 in April 1992 after seeing a man standing, then pacing, outside Ms. Simpson's house around 10:30 or 11 one night.

``I didn't recognize him. I said to myself, what is a man of this description doing outside at this time?'' Colby said.

But moments after he called police, he got a closer look and realized it was Simpson, who frequently visited his children at his wife's house.

``I was embarrassed that I'd called 911 because I didn't feel Mr. Simpson was a threat to me or anyone else in the neighborhood,'' Colby said.

Colby said that Simpson ``seemed to be hesitant and to be attempting to perhaps observe something that may have been occurring inside the house.'' But he said Simpson ``never stepped onto the property or do anything untoward.''

Colby's wife, Catherine Boe, who preceded him to the stand, Simpson had parked around the corner instead of at the curb or in Ms. Simpson's wide driveway.

In cross-examining the couple, defense attorney Robert Shapiro offered an innocent explanation for Simpson's presence, suggesting the former football star might have a meeting arranged with his estranged wife.

And Shapiro suggested that Simpson parked around the corner rather than leave the car under a tree that could drop sticky debris it.

Both witnesses said they did not know whether Ms. Simpson was home that evening.

Ms. Boe said she learned about trouble in the Simpsons' relationship from her visits with the couple and by overhearing them arguing from her kitchen door. The fights, she said, were over the couple's supposed infidelities.

Once, Simpson came to her kitchen when Ms. Simpson wouldn't let him see their children, and ``I fed him a piece of peach cobbler,'' Ms. Boe recalled.

During the kitchen conversation, ``he implied she was upset over his womanizing,'' Ms. Boe said, ``but that was in the past. His womanizing was in the past.''

Another time, she said, she was walking with the Simpsons in the park with the couples' sons, who were good friends, and the Simpsons began arguing.

``He was angry at her for being with another man and she was angry at him for being angry at her,'' Ms. Boe said. ``After awhile, she wouldn't argue anymore. So I was stuck with O.J.''

Jurors and spectators chuckled.

``He said she was sleeping with somebody who'd been staying at her house,'' Ms. Boe said. ``I was sure she wasn't. ... But when I told O.J. that, he scoffed at me, as though to indicate that I shouldn't believe her.

``But I did believe her,'' she said of Ms. Simpson. ``because she had never lied to me.''

On cross-examination, she said the man who was Ms. Simpson's house guest was named Keith and ``Nicole told me he slept in the spare bedroom.''

Keith Zlomsowitch, who became Ms. Simpson's lover at one point, is expected to testify that Simpson once spied on their love-making through a window. That incident, like the one in which Simpson was seen joutside the home, is alleged to have taken place in April 1992. But the exact dates have not been disclosed in court.

Simpson, who is on trial in the June 12 slashing murders of Ms. Simpson and her friend Ronald Goldman, didn't acknowledge Ms. Boe and Colby in court and showed no reaction to their testimony.

Ms. Simpson moved into the rented house in January 1992 and filed for divorce from Simpson in February of that year.

The divorce became final in October 1992, although the couple reconciled later and Ms. Simpson moved back into Simpson's estate for a time. When they split up again, Ms. Simpson moved into a condo, where she was slain.

In another development, it was disclosed in court that a new witness, Leif Tilden, says he saw four men near Ms. Simpson's condominium the night she was slain.

Simpson attorney Johnnie Cochran Jr. complained that the defense had not been told about the witness, who according to ABC is an actor and puppeteer who worked on the TV series ``Dinosaurs.''

Prosecutor Christopher Darden said Tilden had been interviewed by prosecutors within the previous 24 hours. He said the witness' statement would be turned over as soon as it was transcribed.

The prosecutor suggested that Tilden's account does little to bolster the claim of defense witness Mary Anne Gerchas, who allegedly saw four men, some in knit caps, leaving the area of the murders.

In an interview broadcast Thursday, Tilden told ABC's ``Day One'' that he didn't come forward earlier because he hadn't been following the case closely and thought the murders had taken place hours later that night.

Asked if he thought the men he saw while walking his dog in the alley behind Ms. Simpson's condo were in any way involved in the murders, he replied: ``In my ... my gut. No.''

He described the men as white and ``clean cut,'' and said two wore baseball caps, he said. Gerchas had described seeing two white and two Hispanic men and said some were wearing knitted caps.