A veteran Los Angeles police detective was arrested Friday in the 1986 Van Nuys killing of her ex-boyfriend's wife, cracking a cold case packed with the love-triangle twists and forensic drama of a television cop show.

Stephanie Ilene Lazarus, 49, of Simi Valley, was arrested at LAPD headquarters where she worked and booked on suspicion of beating and fatally shooting Sherri Rae Rasmussen, 29, a hospital nursing director. The slaying occurred on Feb. 24, 1986, at the Van Nuys condominium where Rasmussen lived with her husband of three months, John Ruetten.

For years, police believed that two male armed burglars were the lead suspects. But faced with a recent decline in the homicide rate, investigators had time to re-examine the cold case in February. DNA testing eventually led them to Lazarus - who was working on the same floor of police headquarters as the detectives investigating the case.

Lazarus' arrest was the first of a Los Angeles police officer on suspicion of murder in years, and Police Chief William Bratton told reporters he does not believe it sheds negative light on his department. "This individual was investigated and arrested by L.A. police officers who were going where the truth took them," Bratton said. "It reflects very positively on the department.

"It doesn't reflect too well on her, in terms of what we allege that she did, but it has no negative reflection on the department." The arrest stunned Lazarus' LAPD co-workers and her family and neighbors.

Not a suspect early on

Although Lazarus was mentioned as having had a relationship with Ruetten in the original case file, police said she wasn't a suspect at the time because detectives believed Rasmussen had been a victim of armed robbers she had confronted in her home. According to Bratton, Rasmussen had been alone at her home. "Her husband had left for the day, and when he returned in the early evening hours, he found his wife brutally murdered," Bratton said.

"Ms. Rasmussen died as a result of multiple gunshots." At first, police suspected two men linked to a residential burglary a month later that occurred three blocks away. They said in both home-invasion burglaries, armed men had entered security buildings and tried to steal stereo equipment.

They surmised Rasmussen, who had stayed home that day because she had strained her back in an aerobics class, had surprised one or two men who had entered through the unlocked front door. Rasmussen's killing was one of 9,000 unsolved homicide cases in Los Angeles that police said came to the top of the cold case unit's work pile because of DNA evidence in the case.

When investigators reopened the case in February, they analyzed DNA from the crime scene and determined that the killer was a woman, not a man as previously believed. Police declined to disclose further details, saying they feared it could compromise their investigation. Neither police nor Ruetten provided any additional details surrounding the Lazarus-Ruetten romantic relationship.

Gathering DNA evidence

According to reports, detectives had been secretly following Lazarus in recent weeks, attempting to get her DNA to compare with evidence found at the crime scene. Her DNA was eventually taken from a drinking item she discarded, reports said.

Investigators would not say whether they believe Ruetten had any involvement in the slaying. In an e-mail message Friday to the Daily News, Ruetten, who now lives in San Diego, called the developments surrounding his wife's killing a "very difficult time."

"I have been supporting the police investigation for some time and will continue to do so," he said. "I have no other comments." LAPD officers Friday morning searched the Simi Valley home Lazarus shared with her husband, Scott Young, and their young daughter, whom neighbors said was adopted about two years ago. Young, also an LAPD officer, was called to the home from work and cooperated with the officers, letting them inside with his key, according to LAPD Lt. Mark Tappan, who was at the Simi Valley home. "I can't imagine what was going through his mind," Tappan said. "It must be racing a mile a minute."

The LAPD has "no reason to believe he had any prior knowledge of the murder," he added. Tappan, who works across the hallway from Lazarus on the third floor of Parker Center, said there was extreme secrecy surrounding the case until the arrest. He said he and other officers were sent to the Simi Valley location around 8 a.m. Friday with no knowledge of what they were investigating.

When officers arrived at Lazarus' home, they opened up a sealed package of documents they had been given - and that was when they first learned of the case, he said. "We were in the dark up until this morning, because of the very sensitive nature of the investigation," Tappan said.Neighbor Dallas Preece, who lives directly across the street from Lazarus, said he sees the family out in the neighborhood almost every day. "It's a shock. Really you have to feel for Scott and the little girl they just adopted," Preece said. "When you're young, you do things that are foolish as hell - not this bad - but they come back to haunt you. I hope it's not true." Lazarus investigated art theft for the LAPD. Deputy Chief Charlie Beck, who oversees the detective bureau and who was Lazarus' boss, said the arrest took an emotional toll on her colleagues.

"Robbery-Homicide is on the third floor, commercial crimes is right next door," Beck said. "So this is one side of the hallway investigating a member of another. This is very difficult. "We all knew her. Anytime you've known someone for 26 years and known that person for that long and their family, it's going to be hard not to be affected by it." Beck said investigators expect to submit the case Monday to the Los Angeles County District Attorney's Office, which will decide whether to file criminal charges. Lazarus was being held without bail at the Los Angeles County jail.Lazarus joined the department in 1983, according to LAPD records. She was a rank-and-file patrol officer in the San Fernando Valley during the time of the slaying, and was later promoted to detective. In 2006 she was assigned to a unit tracking stolen artwork.

Promising career

At the time of her death, Rasmussen had been the nursing director of the critical care unit at Glendale Adventist Medical Center. She had entered college at 16. In her late 20s, she taught at UCLA and lectured internationally on critical-care nursing. "She was brilliant, well-versed, very quiet, and a very, very nice person," recalled Suzette Cardin, former director of coronary care at Glendale Adventist Medical Center, who is now the assistant dean of students at the UCLA School of Nursing.

"We were totally shocked. Now you watch enough 'Law and Order,' you're never shocked." On Friday, Glendale Adventist Medical Center issued a statement saying that Rasmussen was an integral part of the hospital. "Her death was especially tragic and shocking ..." the statement said. "We are relieved that there is finally closure in sight for this case. Our thoughts and prayers go out to the family."

Lazarus attended elementary schools in Inglewood, then Simi Valley. At Sequoia Junior High School in Simi Valley in the mid-1970s, she was a star track and field athlete and basketball player, she told the Daily News during a 1990 junior high reunion. She graduated from Simi Valley High School in 1978, and went on to UCLA, where she graduated with a degree in political science in 1982. In 1990, Lazarus told the Daily News she was a training officer for the LAPD's Drug Abuse Resistance Education Program. In 2006, she scored a high-profile assignment tracking stolen artwork.

Two months ago, the L.A. Weekly reported on the new Art Theft Unit, responsible for all thefts and burglaries targeting fine art in Los Angeles, as well as all forgeries and fakes - the only dedicated cops in the nation devoted to solving art crimes.

The LA Weekly described Lazarus as "a serious Tyne Daly look-alike a la the 'Cagney & Lacey' television series."