Police Focus on Stalking Motive in Simpson Case : Crime: Ex-wife’s answering-machine tapes seized, friends interviewed. Experts cite need to give reason for killings.

Los Angeles police detectives are interviewing friends and associates of Nicole Brown Simpson and have seized copies of answering-machine tapes from her home in an effort to establish that O.J. Simpson pursued his ex-wife with the vengeance of a stalker and that her murder on June 12 was the final act of that pursuit.

During last month’s preliminary hearing for Simpson, prosecutors homed in on his means and opportunity to commit the double murder in Brentwood--chipping away at his alibi, for instance, and introducing evidence that he had bought a knife weeks before the killings.

But they did not address a provocative question in the case: If Simpson did commit the murders, as they allege, what was his motive?

“The prosecution is not legally obligated to prove motive in order to get a conviction,” said Loyola Law School professor Laurie Levenson. “But a question jurors always have is: ‘Why would someone do such a terrible thing?’ . . . Because people think they know O.J. Simpson, and the O.J. Simpson they know would never do such a terrible thing, it will be crucial for the prosecutors to answer that question.”

Simpson has pleaded not guilty to the murders, and his legal team has accused authorities of failing to pursue leads that point to other suspects.

The stalking theory against Simpson was most elaborately detailed in the June 21 grand jury testimony of Keith D. Zlomsowitch, who briefly dated Nicole Simpson in 1992. He told grand jurors that Simpson pursued the couple during that time, showing up at restaurants where they were dining and once spying on them through a window while the two were having an intimate encounter on Nicole Simpson’s couch.

Zlomsowitch said he felt threatened and intimidated by Simpson’s actions, particularly when Simpson confronted him as he was massaging Nicole Simpson’s neck.

Although Zlomsowitch’s testimony could form an important element of the motive case against Simpson, he is not the only person who has been interviewed about the troubled relationship between O.J. Simpson and his ex-wife.

According to sources familiar with the case, several of Nicole Simpson’s friends have been questioned about whether they have knowledge regarding allegations of abuse. Louis Brown, Nicole Simpson’s father, said Wednesday that he and other family members have been in regular contact with authorities and expect to be officially interviewed at some point, but have not been yet.

Police also have launched an exhaustive search for records of calls for help at Simpson’s home, sources said.

“You couldn’t have been a really good friend (of Nicole) and not have been around when O.J. would show up” uninvited, one friend of Nicole Simpson said. “He would come to the table (at a public place), for example, and make his presence known--make comments until one of us made some comment back, like, ‘C’mon O.J., don’t do this.’ Then he’d sit there and stare at her till we all felt uncomfortable enough to leave. It wasn’t like an ‘Oh, poor O.J.’ stare. It was like, ‘I’m watching you.’ ”

Other friends of Simpson’s slain ex-wife said authorities had seized the tapes from her telephone answering machine, which she would use to screen his unwanted telephone calls “when he wasn’t doing well and she didn’t want to deal with him.”

“It was O.J.’s style to go on and on and on,” one friend said. If Nicole Simpson refused to pick up the phone, the friend added, he would leave long messages on her answering machine.

As prosecutors weigh the evidence regarding motive, they confront several potential pitfalls, experts said. If their evidence falls short of proving a motive, the failed effort might make jurors suspicious of the entire case, legal experts said.

In addition, there is no guarantee that Superior Court Judge Lance A. Ito would allow prosecutors to introduce certain kinds of evidence indicating motive.

As a general rule, courts will not admit evidence of prior bad acts, commonly referred to as character evidence. However, courts in some circumstances will admit evidence of such prior acts if they can be used to show motive.

In this case, such evidence might include Zlomsowitch’s testimony and tapes of 911 calls in which Nicole Simpson pleaded for help because a man she identified as her ex-husband was threatening her.

To get the “stalking evidence” or the 911 tapes admitted, Levenson said, the prosecutors would first have to show that the acts are relevant to the murder and then show that the probative value of the evidence outweighs its possible prejudicial impact.

But if prosecutors do not address the issue of motive, that too has risks. Barry Levin, an experienced criminal defense attorney, noted that California allows jurors to infer innocence from the absence of any evidence about motive.

“Motive is powerful evidence for the prosecution,” Levin said. “The absence of motive is powerful evidence for the defense.”

As the police canvass Nicole Simpson’s friends for clues about her relationship with her ex-husband, some of those friends are taking action of their own. Robert W. Peterson, the owner of a Denver private investigative agency, said Wednesday that he has been retained by a group of clients calling itself simply: “Friends of Nicole.”

Peterson said his backers wish to remain anonymous but have instructed him to turn over to authorities any information he uncovers.

In the brief time that he has been working on the case, Peterson said he has talked to witnesses who have information regarding the relationship between O.J. Simpson and his ex-wife. One witness described shouting matches in restaurants and other public places, the investigator said.

That witness is one of several who have been questioned by police and who have said that Nicole Simpson was afraid of her ex-husband, Peterson added.

“She kept on as good terms as she could with him,” Peterson said. “But she was scared to death of him.”

Times staff writers Henry Weinstein and Rebecca Trounson contributed to this report.

* WITNESS DOUBTED: Man has offered false evidence before, police say. A18