It was a murder that prosecutors say was committed in a fit of rage and jealousy and then covered up for more than two decades.

But on Friday, as she was sentenced to 27 years to life in prison for killing her ex-boyfriend’s wife, former Los Angeles Police Det. Stephanie Lazarus masked any emotion, other than a glance and wave in the direction of her mother as she was led away in handcuffs.

The sentencing brought to a close a case that garnered national attention for its sensational story line of a lovelorn cop killing a woman she viewed as a romantic rival and then harboring the dark secret for 23 years. Adding to the drama were acknowledgments that original LAPD homicide detectives overlooked obvious clues that could have implicated Lazarus far earlier.

Los Angeles County Superior Court Judge Robert J. Perry issued the sentence after several relatives of slain 29-year-old nursing director Sherri Rae Rasmussen delivered brief but visceral victim-impact statements.

Speaking first before the packed courtroom, Loretta Rasmussen called her daughter’s murder a “selfish, brutal act” that caused “a pain for which there is no cure.” But in a show of empathy, she also said her “hearts and prayers” went out to the family of the 52-year-old defendant, particularly her mother.

A short time later, Rasmussen’s widower, John Ruetten, choked back emotion several times. He described the first time he met his wife and imagined the “terror and disbelief” she must have felt in the moments before her death. He said he also often thought about how history might have been different if he had never known Lazarus.

“I don’t know if I will ever know how to cope with this appalling fact,” Ruetten said. “There are so many moments and so very many tears.”

Lazarus’ attorney Mark Overland vowed to appeal. Outside court, Steven Lazarus told reporters that “there was a presumption of guilt” against his sister from the outset.

Sherri Rae Rasmussen was shot three times in the chest after being badly beaten in her Van Nuys town home on Feb. 24, 1986, in what police initially believed was a botched burglary. Three months before the attack, Rasmussen married Ruetten, who had dated Lazarus casually for a few years.

Police were committed to a theory that the suspects were two unidentified male burglars, despite pleas from Rasmussen’s father to investigate Ruetten’s ex-girlfriend.

DNA from a saliva sample gathered from a bite mark on the victim’s left forearm would eventually show that the killer was a woman. But it would take a revolution in forensics technology and the open minds of a new generation of LAPD investigators before Lazarus, by then a respected art theft detective, emerged as the prime suspect.

When the trial opened earlier this year, prosecutors told the eight-woman, four-man jury that the case came down to “a bite, a bullet, a gun barrel and a broken heart.” Deputy Dist. Attys. Shannon Presby and Paul Nunez hammered at those points throughout the five-week trial, which included 400 exhibits and testimony from more than 60 witnesses on both sides.

Defense attorney Overland focused on trying to discredit the integrity of the physical evidence, most notably the saliva sample, which he argued had been mishandled and perhaps tampered with over the nearly two decades it sat in a storage freezer. He also said the plastic tube holding the sample had been found poking through the evidence envelope in which it was stored.

The state’s case, Overland said, amounted to circumstantial “fluff and filler” that failed to prove Lazarus’ guilt.

Overland noted that a blood smear from an unidentified man found at the crime scene was analyzed for DNA and did not match Lazarus or Rasmussen, suggesting the possibility of another suspect. And police were unable to find any witness to the killing.

But prosecutors said the defense could not explain how Lazarus’ DNA ended up in the sample tube.

“There are only two possible ways that the defendant’s DNA was there: it was there because she did it or it was there because someone ... planted it,” Presby said, adding that the defense never presented a plausible tampering theory.

In the end, the DNA evidence proved too difficult to overcome. The jury found Lazarus guilty after deliberating a little more than a day.

Although she was sentenced to at least 27 years to life behind bars before she is eligible for parole, state corrections officials have said she could be eligible for parole in 14 years.

andrew.blankstein@latimes.com

richard.winton@latimes.com