(CNN) -- A veteran police detective in Los Angeles, California, was arrested Friday morning on suspicion of killing a former lover's wife in 1986, marking a rare instance in which the department has arrested one of its own, Police Chief William Bratton said.
Stephanie Ilene Lazarus, 49, was on duty Friday morning when she was arrested in the Los Angeles Police Department's downtown headquarters in the slaying of Sherri Rae Rasmussen, Bratton said.
Rasmussen's husband found her bruised body in their Van Nuys condominium on February 24, 1986. She had been shot multiple times, he said.
At the time, investigators thought Rasmussen had been the victim of a fatal robbery, but with few leads, the case languished, Bratton said.
It wasn't until the department's cold case squad started re-examining the case in February that DNA evidence led to Lazarus, a 25-year veteran who had been on the force two years when Rasmussen was killed.
"The current investigation combined with technology available today led to the identification of Lazarus as the suspect in the case," Bratton said. "The investigation revealed that she had had a previous relationship with the victim's husband prior to the murder. DNA processing and analysis provided a key piece of evidence in this investigation."
New analysis of DNA from the crime scene revealed that the suspected killer was female and not male, as investigators previously suspected. Bratton said cold case detectives used surreptitious means to gather current DNA samples from Lazarus, but he did not elaborate.
Bratton commended officers for ensuring the integrity of the case while faced with the difficult task of investigating a colleague they knew.
"They did what was expected of Los Angeles police officers. They went where the truth and the facts as known to them took them," he said. "[It's] painful for them to be reviewing a case, and then determine that the leads were leading to a current member of the police force."
Deputy Police Chief Charlie Beck noted the proximity of the robbery homicide office to the division where Lazarus worked.
"These are folks, one side of the hallway, investigating a member of the other," Beck said. "You can't know a person for that long or their family and not be affected by this."
Lazarus is being held on homicide charges. The case will be presented to the Los Angeles District Attorney's Office on Monday, Beck said.
All About Los Angeles Police Department