Police looking for Margaret Mamer in June 2018 found evidence that transformed a welfare inquiry into a long-running San Francisco murder prosecution.
SAN FRANCISCO, Cal. — Margaret “Maggie” Mamer’s friends went to authorities on June 1, 2018, because they had stopped hearing from her. They knew she had been having problems with a roommate and wanted police to find out what had happened. The report began a chain of events that led officers to a basement storage container the next day and, more than eight years later, ended with Lisa Gonzales being sentenced to 31 years to life for Mamer’s murder.
Gonzales, now 55, received the state-prison sentence Aug. 3 from San Francisco Superior Court Judge Teresa Caffese. A jury had convicted her in April of second-degree murder and found that she personally used a knife in killing Mamer, who was 61. The sentencing brought the central prosecution to a close after years of forensic work, pretrial proceedings and delays. It also provided a final legal judgment in a case that investigators first encountered not as a known homicide, but as the disappearance of a woman from a shared Mission District apartment.
The inquiry escalated sharply on June 2, 2018. According to prosecutors, a person went to police and reported that Gonzales had killed someone, dismembered the body and placed it in a container in the basement of the building on the 200 block of 14th Street. Officers responded to the residence and contacted Gonzales. She allowed them inside and sat with them in the kitchen, where they asked about Mamer’s whereabouts.
Gonzales told the officers that Mamer had once lived in the apartment but had moved to Eureka, prosecutors said. She said she had helped Mamer move out on May 15 and had not seen her since. That explanation did not end the inquiry. Police searched a storage area associated with the building and located a blue container. Inside, they found human remains later identified as Mamer’s. Gonzales was arrested, and the missing-person investigation became a homicide case.
Investigators then turned back to the apartment to determine what had happened before Mamer disappeared. Crime scene personnel processed the bathroom and found Mamer’s blood throughout the area, according to the district attorney’s office. Prosecutors said bleach had been used in an effort to clean the room. An autopsy later concluded that Mamer died from multiple sharp-force injuries to her face, head and chest. The prosecution said Gonzales dismembered Mamer after killing her and put the remains in the basement container to conceal the crime.
A third person who lived in the apartment gave police a timeline that focused attention on May 15. She said Gonzales told her not to use the bathroom when she came home during her lunch break. After work, the roommate noticed a metallic odor in the apartment and heard sawing noises coming from the bathroom for roughly four hours, according to prosecutors. Gonzales was still in the bathroom the following morning. Later, the witness said, the apartment smelled of vinegar and bleach.
Other details from the roommate connected the bathroom to what police later recovered downstairs. A blue container that had been used for laundry was missing, she said, and a hacksaw appeared beneath a sink in the laundry area. Mamer was also gone. When the roommate asked Gonzales where Mamer had gone, prosecutors said Gonzales answered that she had left, “but not the way she wanted to.” The evidence acquired greater significance once officers found Mamer’s remains in a blue container and documented blood in the bathroom.
Investigators also examined what had been happening between Gonzales and Mamer before May. Mamer began renting a room in the apartment in August 2017 for $400 a month, according to court reporting. Gonzales’ public defender said in 2018 that Gonzales had met Mamer through work and offered her housing after Mamer encountered financial and housing difficulties. But the arrangement soon deteriorated. Accounts from the case described disagreements involving rent, household property and Gonzales’ repeated efforts to get Mamer to leave.
By mid-April 2018, Gonzales had given Mamer a 30-day notice to move out. Prosecutors said Gonzales also told coworkers about her frustration. When they discussed legal routes for eviction, Gonzales responded, “No thanks, I’ll do it my way,” according to the district attorney’s office. At trial, the statement became part of the prosecution’s narrative of mounting conflict. Jurors also heard the far more concrete evidence gathered from the apartment, witness accounts and the medical examination.
Gonzales’ first court appearances came within days of the discovery. Her attorney then, Deputy Public Defender Alex Lilien, asked the public and news media not to treat an accusation as a conviction. He described Gonzales as a working single mother and noted that her family had long lived at the 14th Street property. Gonzales later entered a not-guilty plea. Her defense also described the circumstances in which she had first offered Mamer a place to stay and raised questions about their dispute over money and the shared household.
The case did not proceed quickly after that. In the summer of 2018, the defense and prosecution were still awaiting medical examiner findings and reviewing discovery. The autopsy process took time because of the condition in which Mamer’s remains were found, and a detailed report became public in 2019. Gonzales remained jailed while the prosecution continued. The passage of years eventually became part of the public story surrounding the case, with prosecutors repeatedly acknowledging how long Mamer’s family and friends had waited for a trial.
That trial finally reached a verdict in April 2026. After hearing the evidence, jurors found Gonzales guilty of second-degree murder rather than accepting the not-guilty position she had maintained since 2018. They also found true an allegation that she personally used a knife. District Attorney Brooke Jenkins said afterward that the verdict brought accountability in a case that had remained pending for nearly eight years, while prosecutor Melissa Demetral thanked Mamer’s family and friends for their patience.
The sentencing four months later completed the principal trial-court process. Judge Caffese imposed a term of 31 years to life in state prison. Jenkins said Mamer’s loved ones had waited too long for the case to reach that stage and thanked them for continuing to work with prosecutors. The district attorney’s office also credited homicide detectives, crime scene investigators, prosecutors, paralegals and a victim advocate who assisted Mamer’s family while the case remained active.
Viewed from its beginning, the investigation turned on the difference between what police were initially told and what they found. Mamer was first a missing woman whose friends were worried. Gonzales said she had moved to another Northern California city. A search of the property instead led officers to Mamer’s remains, and a search of the apartment found physical evidence that contradicted the explanation that she had simply left. The jury’s 2026 verdict resolved the criminal question that followed that discovery.
Gonzales is now serving the 31-years-to-life sentence ordered Aug. 3. No additional sentencing hearing has been announced in the case. The outcome closes a prosecution whose public record stretches from a missing-person report and a police visit in June 2018 through years of court proceedings to a second-degree murder judgment entered in 2026.
Author note: Last updated September 20, 2026.