A San Rafael woman who stabbed her mother to death last year is not guilty by reason of insanity, a Marin County jury determined Monday.
Tonantzyn Oris Beltran, 30, was charged with murder for the death of Olivia Beltran, 55, in January 2024. The jury heard testimony for four weeks and deliberated for three hours before reaching its verdict Monday afternoon.
The verdict means the jury found that mental illness made the defendant incapable of knowing the attack was wrong.
Marin County Superior Court Judge Geoffrey Howard will have the defendant placed in a psychiatric facility. Her defense attorney, Matthew Siroka, said she will be held indefinitely.
Beltran would have faced 25 years to life in prison if convicted of murder, Siroka said. He praised the jury after the verdict.
“I think that the speed by which they returned their verdict showed that the evidence was strong,” he said.
Beltran family members hugged Siroka outside the courtroom.
“We feel vindicated because we’ve been telling the detectives and the DAs since the day everything happened that my cousin was insane at the time,” Sandra Beltran said.
“I’m amazed by the amount of county resources they decided to spend on this trial, only to have these wonderful, intelligent jurors see the truth,” she said of the prosecution.
The homicide happened at an apartment complex on Cresta Way. Police arrived to find Olivia Beltran lying mortally wounded on a balcony while her daughter stood next to her with a knife.
In April, after reviewing medical evaluations of Tonantzyn Beltran, Howard ruled she was mentally competent to stand trial.
During the trial, the prosecution played a webcam video that Tonantzyn Beltran recorded of the attack. She also streamed the attack live on Facebook. The video was only shown to the jury, but the audience in the courtroom gallery heard it.
Howard allowed the defendant to be excused from the hearing when the video was played.
Dr. Jess Ghannam, a professor and psychological evaluator from the University of California, San Francisco, was one of the specialists who examined the defendant. He testified that she had delusions and acted as if she heard voices.
“I was interacting with a human being who has a profound mental illness,” Ghannam testified.
Throughout the trial, Siroka discussed Tonantzyn Beltran’s history of mental illness. The defense presented evidence that her past included auditory hallucinations, suicide attempts, multiple hospitalizations and mental delusions.
“This case is about trauma and mental illness,” Siroka said. “This case is about a broken family and a broken mind and system that failed to protect her.”
Siroka had the defendant’s sister, Tonatiuh Beltran, give the final defense testimony. He asked if she believed her sister was sane or insane during the attack.
“I know my sister, I know her better than she knows at times,” she said. “What I know to be true is that my sister was 100% insane.”
During his closing argument, Siroka showed a video of San Rafael police detectives interviewing Tonantzyn Beltran after she was arrested.
“You know what you did was wrong, correct?” a detective asked her.
She quickly replied, “How is that wrong?”
Siroka stopped the video and asked jurors, “Is that someone who understands the difference between right and wrong?”
In the prosecution’s closing argument, Deputy District Attorney Roopa Krishna said the attack was premeditated and the defendant had a motive.
“She knew and understood that she hated her mother, and if she did this she was probably going to prison for a long time,” Krishna said.
Krishna referred to the defendant’s therapy records, text messages and police interactions as proof that she resented her mother. She also said the defendant searched online for information on how to purchase a gun.
Krishna emphasized that the defendant was diagnosed with antisocial personality disorder. She told jurors that Beltran knew how to manipulate authorities into placing her in a mental health hold rather than jail.
Siroka countered that his client was also diagnosed with other disorders such as schizoaffective disorder and post-traumatic stress disorder.
Siroka asked the jury to consider whether the defendant tried to hide, flee or conceal her actions after the homicide. He noted that she contacted the police for “backup,” streamed the attack assault online and did not hide evidence.
“We appreciate the time and attention the jury gave to what was obviously a difficult case to be exposed to,” prosecutor Jack Shannon said after the trial ended.
Olivia Beltran was an activist who worked with Marin organizations such as the Grassroots Leadership Network of Marin and the Canal Welcome Center.