BERKELEY, Calif. — A California engineer who was caught on hidden-camera footage pouring toxic cadmium into his co-worker’s water bottle appeared in Alameda County Superior Court on Monday, Oct. 12, to ask a judge to dismiss his felony poisoning conviction so the record would not appear in future employment background checks.
David Xu, 41, pleaded no contest in September 2023 to one felony count of poisoning and received two years of probation — a sentence a judge at the time called “extremely generous.” He completed that probation in March 2026 and is now eligible under California law to petition for expungement, a process that allows a person to withdraw a guilty or no-contest plea and have the case formally dismissed. His victim, Rong Yuan, 50, released the hidden-camera footage publicly just days before the hearing in a direct effort to oppose the petition, and the Alameda County District Attorney’s Office has also filed an objection. The judge had not ruled as of Monday morning.
Yuan told The San Francisco Standard that she first noticed something was wrong in 2017, within months of joining Berkeley Engineering and Research, where Xu had already been working as a metallurgist. She began experiencing persistent nausea, vomiting, hair loss and a sour taste in her mouth. Her condition worsened over nearly two years, sending her to the emergency room multiple times. Yuan said she began to suspect her workplace exposure after noticing her symptoms worsened on days she drank from her water bottle at the office. Her suspicion deepened after her mother, who had traveled from China to help care for her, also fell ill after drinking from the same bottle and noticed the same sour taste. Yuan decided to install a hidden camera near her desk. “My blood was frozen,” Yuan recalled of the moment she first watched the footage back. “I almost died. I experienced death so, so close, so many times.”
The camera captured two separate incidents. On Feb. 11, 2019, it recorded Xu reaching toward the area where Yuan kept her water bottle. A second, clearer recording on March 4, 2019, showed Xu entering her workspace, unscrewing the bottle cap, and pouring a substance from a small white container into the water. He then returned briefly to reposition the bottle before walking away. Yuan turned both recordings and water samples over to Berkeley police. Laboratory testing found cadmium concentrations in her bottle reaching approximately 3.5 million times the federal drinking-water limit, according to a lab report reviewed by The San Francisco Standard. Blood tests also confirmed elevated cadmium levels in Yuan and both of her parents, who had consumed water she brought home from work. Cadmium is classified as a carcinogen by the World Health Organization and can cause severe kidney damage, weaken bones and harm the respiratory system. The Agency for Toxic Substances and Disease Registry warns that consuming high concentrations can cause severe gastrointestinal distress and, in extreme cases, death.
Berkeley police arrested Xu at his Lafayette home on March 28, 2019. Prosecutors charged him with premeditated attempted murder and two felony counts of poisoning — charges that collectively carried the possibility of a life sentence. He posted $2 million bail and was released. Court records reviewed by The Berkeley Scanner show he spent 10 days in jail during the early stages of the proceedings and served part of the following years under electronic monitoring. The criminal case stalled in court for four years. In September 2023, then-Alameda County District Attorney Pamela Price’s office offered a plea deal that eliminated the attempted-murder charge and one of the two poisoning counts. Xu pleaded no contest to the single remaining felony. When Xu appeared for sentencing in March 2024, Judge Kimberly Colwell increased the probation term from the one year originally negotiated to two years. Reviewing the terms on the record, Colwell described the agreement as “extremely generous, considering everything in this case,” according to a San Francisco Chronicle review of the sentencing transcript. Before concluding the hearing, Colwell addressed Xu directly: “Please do not touch any poison at all. Ever. Ever.” Price was subsequently recalled by Alameda County voters in 2024 and replaced by District Attorney Ursula Jones Dickson.
Yuan has continued to document the health consequences she attributes to the poisoning. On Oct. 8, just days before the expungement hearing, she published a research paper detailing seven years of medical complications affecting herself and both of her parents. She had originally sought nearly $500,000 in restitution from Xu. Instead, the court ordered him to pay $7,058, an amount based on a toxicology report that concluded the poisoning would not cause long-term health problems. Yuan disputes that finding, telling The San Francisco Standard she is still unable to work full time. She dedicated the research paper to her father, who died of heart failure after his health declined sharply following his cadmium exposure. “Before poisoning, my father had only well-controlled hypertension, walked six miles daily, and could carry a 50-pound bag of rice to the second floor,” Yuan told the outlet. By late last year, she said, he was “bedbound, unable to eat.” Yuan said the financial and physical toll of the case has been compounding. Despite the gravity of the original charges, Xu served only one day of credited jail confinement under court records reviewed by SFGATE, with the imposition of his sentence suspended.
Under California law, a person who successfully completes probation on a qualifying conviction may petition the court to have the case dismissed. The process is commonly called expungement, though it does not completely erase the criminal record — certain government agencies and professional licensing authorities retain the ability to access it. For most private employers conducting routine background checks, however, the conviction would not appear. That distinction is at the center of Yuan’s opposition. She told The San Francisco Standard she fears Xu could obtain work in fields where access to hazardous materials is routine, without employers knowing about his conviction. “This legal system already failed me,” Yuan said. “This is my last resort.” She planned to address the court directly at Monday’s hearing, exercising her right as a victim to speak before any ruling is made. Court records confirmed the district attorney’s office had filed a formal objection to Xu’s petition. Both Xu and Yuan hold doctorate degrees from UC Berkeley and worked together as metallurgists, professionals who study the properties and processing of metallic elements, at Berkeley Engineering and Research on Gilman Street in Berkeley.
As of Monday, Oct. 12, the Alameda County Superior Court had not yet issued a ruling on Xu’s expungement petition. Yuan attended the hearing and addressed the court. The judge’s decision, once issued, will determine whether Xu’s single felony poisoning conviction remains visible on standard background checks or is formally dismissed under California’s expungement statute. The district attorney’s office opposition and Yuan’s victim statement remain part of the court record the judge must weigh before ruling.