LA policewoman found guilty of love rival's murder in 1986

Bite mark on victim's arm provides crucial DNA evidence after cold case review

A former police detective faces life in prison after being nailed for murder by a bite mark on her victim's arm.

Stephanie Lazarus, 51, thought she had got away with the murder of her lover's wife 26 years ago but was caught when a cold case review picked up traces of DNA from a bite mark.

When she killed Sherri Rasmussen, a 29-year-old nursing supervisor, in 1986 she used her knowledge as a Los Angeles policewoman to avoid leaving clues to her identity. There were no fibres, fingerprints, hairs or blood spots to tie her to the murder scene.

DNA fingerprinting was in its infancy when she bludgeoned and shot Ms Rasmussen, who three months earlier had married Lazarus's lover, John Ruetten. It was first used in a criminal case in 1985 in the UK in an effort to identify a killer – three years later Colin Pitchfork was convicted of two murders.

Detectives initially thought the murder must have been committed during a robbery and they linked it to a robbery on a woman that had recently taken place close to the scene. Only 20 years later did DNA testing, by then in widespread use, reveal the killer was a woman and the inquiry team began to look at Lazarus as a suspect.

They followed their colleague on a shopping trip and when she discarded a cup after drinking from it they recovered it and found that her DNA matched the sample from the victim's body. It remains unclear if Lazarus went to Ms Rasmussen's apartment intent on murder or if a confrontation turned violent but she beat her rival over the head and then shot her three times in the chest.

Police Chief Charlie Beck, who had worked closely with Lazarus, apologised to the Rasmussen family for the long delay in solving the case. "I am truly sorry for the loss of your wife, of your daughter," he 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. This case was a tragedy on every level. The LAPD family felt a sense of betrayal to have an officer commit such a terrible crime."

The Rasmussen family has filed a wrongful death lawsuit against the LAPD and the city of Los Angeles. John Taylor, a lawyer for the family, said after the a guilty verdict was returned: "The family is relieved that this 26-year nightmare has concluded with the positive identification of the person who killed their daughter."

Lazarus and Mr Ruetten became lovers for a year after they graduated from college but in court he testified that he never intended to marry her. "It was clear she was very upset that I was getting married and moving on," he said.

The defendant's lawyer, Mark Overland, ridiculed the claim of a fatal attraction between Lazarus and Ruetten, saying she never tried to reunite with him after his wife was gone. He suggested that the DNA evidence had been packaged improperly and that the evidence could have been tampered with.

District attorney Steve Cooley said: "Had it not been for DNA the case might never have been solved."