Lisa Gonzales was convicted of killing Margaret Mamer in 2018 after mounting tensions over rent, household disputes and an attempted eviction.

SAN FRANCISCO, Cal. — A San Francisco woman has been sentenced to 31 years to life in state prison for the 2018 murder of a roommate whose disappearance led police to a Mission District apartment, where investigators found her remains hidden in a basement storage container. Lisa Gonzales, 55, received the sentence Aug. 3 after a jury convicted her in April of second-degree murder and found that she personally used a knife in the killing of 61-year-old Margaret “Maggie” Mamer.

The sentence closes the central criminal proceedings in a case that began more than eight years earlier with a missing-person report and a tense shared-living arrangement on 14th Street. Prosecutors said Gonzales had repeatedly wanted Mamer out of the apartment before the killing. Evidence presented at trial included statements Gonzales made about removing Mamer, observations from another roommate, blood evidence recovered from the bathroom and Gonzales’ account to police that Mamer had moved away. A jury rejected Gonzales’ earlier not-guilty plea and convicted her after a trial this spring. Superior Court Judge Teresa Caffese imposed the 31-years-to-life term.

Mamer had moved into the home in August 2017 after she and Gonzales met while working at Whole Foods, according to court reporting from the early stages of the case. Gonzales’ public defender said at the time that Gonzales had offered Mamer a room when Mamer was having housing difficulties. They agreed on rent of $400 a month. Their relationship deteriorated over the following months. Prosecutors said Gonzales became upset about household problems and Mamer’s refusal to leave, while Gonzales’ attorney said in 2018 that Mamer had a history of failing to pay rent. Those disputes became part of the prosecution’s account of what preceded the killing.

By mid-April 2018, Gonzales had given Mamer 30 days to move out, according to prosecutors. Gonzales also discussed the situation with coworkers. When they told her about ways she could pursue a legal eviction, prosecutors said Gonzales answered, “No thanks, I’ll do it my way.” The remark later became a notable piece of the government’s account of escalating tension between the two women. It did not stand alone, however. Jurors heard a broader collection of evidence concerning what happened inside the apartment, what another roommate observed and what police discovered weeks later.

Another woman living in the apartment supplied some of the most important testimony about the period around Mamer’s disappearance. On May 15, 2018, prosecutors said, Gonzales told that roommate not to enter the bathroom when she returned home during a lunch break. Later, the roommate noticed an unusual metallic odor in the apartment and heard sawing sounds coming from the bathroom for about four hours. Gonzales was still in the bathroom the next morning, according to the account presented by prosecutors. When the roommate later returned, the smell had changed to vinegar and bleach.

The roommate also realized that a blue plastic container she had used for dirty clothes was missing. She saw a hacksaw under a sink in the laundry area, according to trial evidence summarized by prosecutors. When she asked Gonzales what had happened to Mamer, prosecutors said Gonzales told her that Mamer had left, “but not the way she wanted to.” The statement, the missing container and the conditions inside the apartment would later take on greater importance once Mamer’s friends raised alarms about not hearing from her.

Mamer was reported missing on June 1, 2018, after friends who knew about tensions at the apartment became concerned when they could not reach her. The next day, a person went to police and reported that a killing may have occurred at the 14th Street residence and that a body had been concealed in a container, according to the San Francisco District Attorney’s Office. Officers went to the apartment and contacted Gonzales. Prosecutors said she invited them inside and told them Mamer no longer lived there.

Gonzales told officers that Mamer had moved to Eureka and that she had helped her leave on May 15, prosecutors said. Police then searched a storage area connected to the building. Inside a blue container, officers found human remains that were later identified as Mamer’s. The discovery turned what had begun as a search for a missing woman into a homicide investigation. Gonzales was arrested, and the case moved quickly into San Francisco Superior Court, though it would take years before a jury ultimately heard the evidence.

Investigators processed the apartment after the discovery. The San Francisco Police Department’s crime scene team found Mamer’s blood throughout the bathroom despite evidence that the room had been cleaned with bleach, prosecutors said. Medical examination later established that Mamer died from multiple sharp-force injuries to her face, head and chest. Prosecutors presented evidence that her body was dismembered after her death in an effort to conceal the killing. The government’s case tied the physical evidence to the roommate’s description of the closed bathroom, prolonged sawing sounds, chemical odors, missing container and hacksaw.

Gonzales initially faced the accusation in court in June 2018. At her first appearance, her public defender described her as a working single mother whose family had lived for decades in the same rent-controlled apartment. She later pleaded not guilty. Early court proceedings were slowed in part while attorneys waited for medical examiner findings and other evidence. Gonzales remained in custody as the prosecution developed a case that would ultimately depend on forensic evidence, witness accounts and statements attributed to Gonzales before and after Mamer disappeared.

The apartment itself had a complicated housing history for Gonzales. Four years before Mamer’s death, Gonzales had publicly protested an effort to evict her from the Mission District home. Reporting from 2018 said tenant advocates joined her in protesting at a real estate office. That history later became an unusual backdrop to the prosecution’s evidence that Gonzales had herself become frustrated by a roommate who would not leave. The prior eviction fight did not determine Gonzales’ guilt, but it formed part of the documented history of the residence and of Gonzales’ long connection to the property.

After years of pretrial proceedings, the case reached a jury in 2026. Jurors found Gonzales guilty of second-degree murder and also found true an allegation that she personally used a deadly weapon, identified by prosecutors as a knife. District Attorney Brooke Jenkins said after the verdict that Mamer’s relatives and friends had waited almost eight years for the case to reach that point. Assistant District Attorney Melissa Demetral, who prosecuted the case, thanked jurors for reviewing difficult evidence and credited police investigators and Mamer’s family and friends for their work and patience.

The sentencing in August increased the punishment beyond the 16-years-to-life term that had been cited immediately after the April verdict. Judge Caffese ultimately ordered Gonzales to serve 31 years to life in state prison. Jenkins said the sentence would hold Gonzales accountable and again acknowledged the length of time Mamer’s relatives and friends had waited for the prosecution to conclude. The district attorney’s office said its case was supported by the homicide investigation, crime scene work and evidence developed during the years the matter remained pending.

With the sentence imposed, Gonzales is now serving a state-prison term of 31 years to life for Mamer’s murder. The district attorney’s office has announced no further trial or sentencing proceeding in the case. The Aug. 3 sentence marks the principal resolution of a prosecution that began with Mamer’s disappearance in June 2018 and ended eight years later with a murder conviction and an indeterminate life sentence.

Author note: Last updated September 20, 2026.