Los Angeles (CNN) -- A California judge sentenced a retired Los Angeles Police detective Friday to 27 years to life in prison for murdering her ex-boyfriend's wife in a jealous rage more than two decades ago.
Stephanie Ilene Lazarus, 52, was convicted of biting and shooting Sherri Rasmussen, 29, in her townhouse in the Van Nuys neighborhood of Los Angeles in 1986.
Lazarus, who rose through ranks of the Los Angeles Police Department and became a veteran art theft detective, could be eligible for parole in 22 years. Los Angeles Superior Court Judge Robert Perry gave Lazarus credit for time served in jail since her arrest at LAPD headquarters in June 2009.
A jury convicted her in March of first-degree murder.
Friday's sentence was the maximum under state law, prosecutors said.
Lazarus was charged with staging the crime scene to look like a burglary gone bad, and police long believed that Rasmussen was the victim of two male burglars.
The 1986 case went cold for years. Then it was reopened in 2004 and again in 2009, when DNA from a bite mark on the victim's arm came back as a match to the detective.
When Lazarus became a suspect, homicide detectives faced "special challenges as Lazarus' office was located next door to the detectives who were now investigating her," police said in a statement in March.
Rasmussen, a hospital nursing supervisor, was the new bride of John Ruetten, who had been Lazarus' college sweetheart. Married for just three months, Ruetten found his wife's body when he returned home from work. Rasmussen was brutally beaten and shot three times in the chest, authorities said.
Los Angeles County deputy prosecutors Shannon Presby and Paul Nunez submitted a written statement to the court prior to the sentencing, according to the prosecutor's office.
"Lazarus has never taken responsibility for her acts," the prosecutors wrote. "Lazarus has never expressed any regret or remorse for her actions. Lazarus' profound narcissism led her to kill and continues to motivate her denial of responsibility. This unrepentant selfishness poses a real and significant danger to any person whose interests conflict with Lazarus' egotistic desires."
Before the sentencing Friday, Rasmussen' mother, Loretta, told the court that her family has endured "extreme pain" over her daughter's murder.
"Every day we miss her laughter and her love," the mother told the judge.
In his remarks to the judge, a tearful Ruetten said Rasmussen was "just trying to save her own life" on the day of her murder.
"I just can't bear thinking about these moments," Ruetten told the court.
After the sentencing, Lazarus, manacled and dressed in a jail jumpsuit, waved and smiled to an apparent loved one in the courtroom gallery as she was escorted back to jail, carrying a folder.
Following Lazarus' conviction in March, Los Angeles Police Chief Charlie Beck said the case was "a tragedy on every level."
"Not only did the family of Sherri Rasmussen lose a wife and a daughter, a life that can never be returned, but also the LAPD family felt a sense of betrayal to have an officer commit such a terrible crime," Beck said in a written statement.
"I am also sorry it took us so long to solve this case and bring a measure of justice to this tragedy," he said.
Rasmussen, director of nursing at Glendale Adventist Medical Center, was a tall, athletic 29-year-old with a pretty smile.
At the time of the slaying, Lazarus was in her second year with the Los Angeles Police Department. The killing occurred on February 24, 1986, a Monday. Lazarus had taken the day off; Rasmussen had called in sick that morning. Authorities estimate she died before lunchtime.
Prosecutors argued that Lazarus was in love with Ruetten and distraught when she learned he married someone else.
During the trial, Ruetten testified he casually dated Lazarus after college, but he never considered her a girlfriend and dated other women while seeing her. Lazarus eventually married a Los Angeles Police detective and the couple adopted a daughter.
According to prosecutors, the key to unlocking Lazarus' dark secret lay for years on the back shelf of an evidence freezer in the coroner's office. In a vial inside a sealed evidence envelope was a cotton swab. On that swab, prosecutors say, was DNA taken from saliva from the bite wound on Rasmussen's left forearm.
Testing in 2005 revealed the assailant was a woman. Some detectives, however, clung to the burglary theory and focused their inquiries on known female prowlers.
But from the beginning, the victim's family had pointed to an ex-girlfriend of Ruetten's who was a cop, and as the DNA testing advanced, undercover police followed Lazarus to a Costco store and retrieved a discarded soda from a trash can. Saliva traces from the straw matched the bite mark DNA, and she officially became a suspect.
Lazarus was confronted, and another sample was taken from her shortly before her arrest. Tests revealed the DNA found in the bite mark on Rasmussen's left forearm belonged to Lazarus.
Deputy Assistant District Attorney Presby told jurors during the trial that the chance of the killer being anyone else is "one in 1.7 sextillion."
To avoid botching an undercover investigation of one of their own, LAPD officials carefully devised a plan to arrest Lazarus. On June 5, 2009, Detective Daniel Jaramillo from the department's robbery-homicide division approached Lazarus at her desk in the department's headquarters and asked her to accompany him downstairs to the department's jail facility, where she would not be able to bring her gun.
He told Lazarus he needed her help interrogating a man who claimed to have information on stolen art, Lazarus' specialty in the detectives unit. A nearly hour-long recorded interview followed.
After one of the detectives alludes to the evidence that implicated her in the killing, Lazarus said, "Am I on 'Candid Camera' or something? This is insane. This is absolutely crazy. This is insane."
Minutes later she walked out of the interview room, only to be stopped, handcuffed and told she was under arrest in the murder of Sherri Rae Rasmussen.
Lazarus's attorney, John Overland, has argued in court that the crime scene evidence from 1986 was mishandled and tainted years ago and couldn't be trusted.
CNN's Ann O'Neil contributed to this report.