The relationship between Lisa Gonzales and Margaret Mamer deteriorated months after Gonzales offered Mamer a low-cost room in her longtime Mission District home.
SAN FRANCISCO, Cal. — Lisa Gonzales once offered Margaret “Maggie” Mamer a room in the Mission District apartment where Gonzales’ family had lived for decades. Within months, Gonzales wanted Mamer gone. That failed living arrangement became the background to a 2018 killing that would take nearly eight years to reach a jury and eventually send Gonzales to state prison for 31 years to life.
Superior Court Judge Teresa Caffese imposed the sentence Aug. 3 on Gonzales, 55, following her April conviction for second-degree murder in Mamer’s death. Jurors also found that Gonzales personally used a knife. Prosecutors said Mamer, 61, was killed after tensions developed over her continued presence in the apartment, including disputes about rent and household issues. The case became notable not simply because of the way Mamer’s body was concealed, but because evidence at trial traced the deterioration of the women’s relationship before she disappeared.
Mamer moved into the apartment in August 2017. Early court reporting said she and Gonzales had met through their jobs at Whole Foods. Gonzales’ public defender said after her arrest that Mamer had been struggling with housing and that Gonzales offered her a room in the 14th Street residence. The rent was set at $400 a month. The defense portrayed the original arrangement as an attempt to help Mamer when she needed a place to live, while prosecutors later focused on what happened after relations inside the apartment deteriorated.
Within months, disagreements emerged. Court accounts from 2018 referred to misplaced or broken household items, while Gonzales’ attorney said Mamer had a history of not paying rent. Prosecutors said Gonzales repeatedly demanded that Mamer move. In mid-April 2018, Gonzales gave her a 30-day notice to leave. Mamer remained at the property. Those tensions later became an important part of the chronology prosecutors presented to jurors, but the murder conviction rested on the full body of evidence rather than on the housing disagreement alone.
Prosecutors said Gonzales discussed the problem with coworkers before Mamer died. Colleagues suggested legal ways she could pursue an eviction. Gonzales replied, “No thanks, I’ll do it my way,” according to the district attorney’s office. The statement took on significance after Mamer disappeared, but at the time it was part of an ongoing disagreement over ending the living arrangement. The state later used it alongside witness testimony, forensic findings and Gonzales’ statements to investigators to establish the events surrounding the killing.
The relationship reached a critical point in mid-May. Another roommate said Gonzales told her during a May 15 lunch break that she should not enter the bathroom. Later that day, the roommate noticed an unusual metallic smell and heard sawing noises from the bathroom for about four hours, according to prosecutors. Gonzales remained in the bathroom the next morning. Afterward, the roommate smelled vinegar and bleach and realized that a blue container she used for laundry was missing. She also saw a hacksaw beneath a sink.
Mamer was no longer in the apartment. When the third roommate asked Gonzales where she was, prosecutors said Gonzales replied that Mamer had left, “but not the way she wanted to.” Mamer’s friends also lost contact with her. On June 1, they reported her missing, telling authorities they were aware of tensions involving Mamer and Gonzales. The next day, another person approached police and alleged that a homicide had taken place and that a body had been put into a container in the building’s basement.
Police went to the apartment and spoke with Gonzales. Prosecutors said she invited the officers inside but gave them a different explanation for Mamer’s absence. Gonzales said Mamer had moved to Eureka and that she had helped her relocate on May 15. Officers searched the building’s storage area and found a blue container holding human remains later identified as Mamer’s. The discovery led police to treat the residence as a homicide scene and provided an immediate connection to the container the other roommate had reported missing.
Forensic work further challenged the account that Mamer had simply moved away. Police crime scene investigators found Mamer’s blood throughout the bathroom, even though prosecutors said bleach had been used to clean the room. An autopsy found that Mamer suffered multiple sharp-force injuries to the face, head and chest. Prosecutors said she was dismembered after she was killed and that her body was placed in the container to conceal what had happened.
Gonzales was arrested and appeared in court in June 2018. She later pleaded not guilty. Her public defender at the time urged reporters to remember that the criminal charge remained an allegation and described Gonzales as a hardworking single mother. He also emphasized the circumstances under which Gonzales had originally allowed Mamer to live in the apartment. The prosecution rejected suggestions that Mamer’s rent history diminished the seriousness of the case. Those opposing accounts reflected the early stage of proceedings, years before a jury would determine Gonzales’ guilt.
There was another housing-related chapter in Gonzales’ history with the property. In 2014, Gonzales and tenant advocates had protested an attempt to evict her from the same Mission District apartment. She had deep roots there, with reporting indicating that her family had lived in the building since the late 1960s. Four years later, prosecutors alleged that Gonzales’ frustration centered on her inability to remove Mamer from the home. The earlier dispute was background rather than proof of the later homicide, but it highlighted how housing conflicts intersected with different periods of Gonzales’ life at the address.
The murder case then moved slowly. Early hearings were affected by the wait for the medical examiner’s conclusions and by the large amount of material attorneys needed to review. Gonzales remained in custody. The medical examiner’s detailed report became public in 2019, and the prosecution continued toward trial. By 2026, many years had passed since officers first entered the building looking for Mamer. The district attorney’s office said Mamer’s family and friends had endured that delay while the case remained pending.
When the trial finally concluded in April, jurors convicted Gonzales of second-degree murder and found true the knife-use allegation. District Attorney Brooke Jenkins said the verdict provided accountability after almost eight years. Assistant District Attorney Melissa Demetral, who prosecuted the case, thanked police and jurors for their handling of difficult evidence and recognized Mamer’s family and friends for remaining involved through the lengthy proceedings. Gonzales remained in custody while the court prepared for sentencing.
The Aug. 3 hearing brought the criminal case to its major conclusion. Judge Caffese sentenced Gonzales to 31 years to life, a term that will keep her in state prison for decades before any possibility of release under the sentence. Jenkins said the court’s decision followed a long wait for Mamer’s relatives and friends. The district attorney’s office credited San Francisco police homicide investigators, crime scene personnel and prosecutors with developing the evidence ultimately presented to jurors.
The sentence transformed a housing dispute that had once involved rent, damaged or missing items and an unwanted roommate into the final procedural chapter of a murder prosecution. Mamer entered the apartment in 2017 as a tenant paying a relatively modest monthly rent. Less than a year later, she was dead. Gonzales, the woman who had first given her a place to live and then sought to make her leave, is now serving a 31-years-to-life sentence for her murder.
Author note: Last updated September 20, 2026.