A veteran Los Angeles homicide detective accused of misconduct in a 22-year-old murder case has decided to retire amid continuing scrutiny of his investigation and a questionable letter he later wrote to the state parole board to keep the man he helped convict in prison.

Lt. Andrew Monsue, 57, worked his last day as supervisor of detectives in the LAPD’s Central Division on Friday. His retirement will take effect July 9, after 31 years of service and what he says have been more than a thousand homicide investigations.

His retirement follows an article in The Times last month that detailed new evidence and findings that contradict the prosecution’s case against Bruce Lisker, 39, now serving a life sentence for murdering his 66- year-old mother in the family’s Sherman Oaks home in March 1983. Even the prosecutor, now retired, said he has “reasonable doubt” about Lisker’s guilt.

After the article appeared, both the LAPD’s inspector general and a monitor appointed by a federal judge to oversee LAPD reforms have said they are reviewing the Lisker case.

Lisker filed a complaint against Monsue with the LAPD’s Internal Affairs Division two years ago, accusing him of conducting a sloppy, dishonest investigation in which he discounted another suspect who gave false information about his whereabouts at the time of the killing and had a history of violence.

Lisker also accused the detective of lying to state parole officials years later in an effort to block his parole. Lisker said Monsue wrote a letter to the parole board in 1998 stating that the new owners of the house where the slaying took place had reported finding $150 in the attic above Lisker’s old bedroom.

Although Lisker was taken into custody at the scene of the slaying, police never recovered the money that was reportedly missing from his mother’s purse. Based on Monsue’s investigation, the prosecution’s theory at trial was that a teenage Lisker beat and stabbed his mother, Dorka, after she caught him stealing money from her purse in order to buy drugs.

The discovery by the new homeowners, Monsue wrote to parole commissioners, “confirmed our initial theory that Mr. Lisker had in fact robbed his mother.”

A private investigator working for Lisker’s defense team, however, obtained a sworn statement from the homeowner stating that neither he nor his wife had found any money or told Monsue they had.

Despite the homeowner’s statement, Monsue’s supervisor, Capt. James Rubert, responded to Lisker on behalf of the LAPD last year and said that his complaint had been deemed “unfounded,” meaning that department investigators had proved that no misconduct had occurred. He also informed Lisker that other aspects of his complaint had already been considered by various courts and therefore were not worthy of further scrutiny.

Rubert, a 34-year veteran, also retired in recent weeks. He announced his intention to do so before the problems with the Lisker case became public.

Monsue was not available for comment Monday.

During a 90-minute interview with The Times in November, Monsue denied any wrongdoing in the Lisker case and said he was fed up with the continued scrutiny of his actions.

“It’s mildly interesting to me that they are calling me a liar, OK? What does it prove?” Monsue said. “We’ve got a lying, cheating, murdering son of a bitch in prison that’s making these allegations ... and you’re sitting here questioning my credibility.... That upsets me.”

The detective also hinted that he might retire because of the renewed interest in the case.

“I’ve got nothing to lose now,” he said. “I’ve got my 30 years on, OK?.... My pension is in the bank. But I’m getting very tired of trying to explain this over and over and over and over.” Monsue, a former Marine who served in Vietnam, said that one of his most notable cases was in 1990, when he led the investigation into a fatal shooting at the Hollywood Hills estate of Marlon Brando. The actor’s son, Christian, was charged with killing his half-sister’s Tahitian boyfriend. He ultimately pleaded guilty to voluntary manslaughter.

As an investigator, Monsue said he had a fundamental rule: “keep it simple, stupid,” meaning that people were often murdered by someone close to them.

When Dorka Lisker was killed, he said, her son, who called for help from the scene of the crime, was the obvious suspect at the time. Monsue remains convinced of his guilt today.

A self-described “dinosaur,” Monsue occasionally bruised the feelings of fellow workers and citizens with his bristly demeanor.

In 1999, a citizen complained that Monsue jabbed a finger in his face. His supervisor counseled him to tone down his “mannerisms.”

In 2002, the city paid $1.25 million to settle a lawsuit filed by a female LAPD sergeant who once complained that Monsue made racially insensitive remarks, and that the LAPD punished her for objecting. The woman quoted Monsue as saying that “the white man is at a disadvantage” because of affirmative action. He denied it.

Monsue sought his own promotion within the department with dogged persistence. He took the oral exam for supervising detective 54 times before he was selected for the position.

Since Lisker filed his complaint against Monsue on June 9, 2003, new evidence and findings developed by his private investigator, the internal affairs officer and Times reporters have further undermined the prosecution’s case against him.

A test by an analyst from the LAPD’s Scientific Investigation Division revealed that a bloody footprint found at the crime scene and attributed to Lisker at trial was not made by Lisker’s shoes.

At the request of Times reporters, the same analyst determined that a shoe-print impression found on the victim’s shaved head during an autopsy was “similar in size and dimension” to a mystery footprint in the bathroom.

The findings bolster Lisker’s claim that he came home to find his mother on the brink of death, and that the assault was the work of an unknown intruder.

The retired prosecutor, Phil Rabichow, has also abandoned a key argument made at trial: that Lisker could not have seen his mother lying on the floor through windows at the back of the house, as he claimed, because his view would have been blocked by furniture and an interior stone planter.

Following a crime scene reenactment with Times reporters, Rabichow acknowledged that Lisker might have been able to see his mother lying in the home’s entryway.

After the Times article last month, at least seven jurors said they would have acquitted Lisker if they had known about the new evidence and findings at the time of the trial in 1985.

Lisker has a habeas corpus case pending in federal court in Los Angeles.

As for Monsue’s retirement, Lisker said he was pleased to hear that he was calling it quits. “That’s fantastic,” Lisker said in a telephone interview from Mule

Creek State Prison, where he’s serving a life sentence. “I’m not surprised. He’s going to try and duck and get out of there and not be as conspicuous a target. He doesn’t deserve his pension.... At least he can’t do it to anyone else. In a way, society is a little bit safer than it was a few days ago.”