A California chemical engineer who pleaded no contest to poisoning a colleague is seeking to have his felony conviction dismissed after completing probation, following a case in which hidden camera footage appeared to show him tampering with his coworker’s water bottle.
David Xu, a metallurgist at Berkeley Engineering and Research (BEAR), was accused of adding cadmium, a toxic heavy metal, to colleague Rong Yuan’s food and water over a period of nearly 18 months between 2017 and 2019. Yuan suffered serious health problems during that time, including persistent vomiting, hair loss and an unusual sour taste in her mouth. Her condition led to repeated hospital visits as she tried to determine what was making her ill.
Yuan later told The San Francisco Standard that watching the surveillance footage for the first time left her deeply shaken. “My blood was frozen,” she said. “I almost died. I experienced death so, so close so many times. I cannot let him go.”
The case began to unravel after Yuan became suspicious that someone at work might be tampering with her food and drinks. She installed a hidden camera at her workplace, and the footage appeared to show Xu approaching her desk and pouring a substance into her water bottle on separate occasions. Yuan turned the recordings over to police, prompting an investigation that led to Xu’s arrest in March 2019.
When Yuan reported severe vomiting to colleagues on November 27, 2018, and said she needed to take a sick day, Xu responded by suggesting she work from home until she felt better. According to The San Francisco Standard, he also wrote, “I think BEAR is moldy.” At the time, Yuan was still struggling to identify the cause of her symptoms.
Following Xu’s arrest, he was released on $2 million bail. His home confinement conditions were subsequently modified several times, and his travel restrictions were eventually lifted, according to The San Francisco Standard.
The criminal case took a significant turn in late 2023, when a plea agreement offered by then-Alameda County District Attorney Pamela Price resulted in the attempted murder charges being dropped. Xu pleaded no contest to one felony count of poisoning and was sentenced to two years of probation. He received credit for one day served in jail.
Yuan had sought nearly $500,000 in restitution for the harm she said she suffered. However, the court ordered Xu to pay $7,058 in restitution, a substantially smaller amount than she had requested.
Xu completed his probation in March 2026 and is now asking a court to dismiss his felony conviction under California’s expungement law. The request comes after he fulfilled the terms of his probation, bringing the case to another stage focused on the consequences of his conviction.
Under California law, judges generally must grant a dismissal to eligible defendants who have completed probation and met the applicable legal requirements. Such a dismissal does not erase the underlying case or mean that the conviction never occurred. Xu’s request therefore concerns the legal status of his record following the completion of his sentence, rather than a reconsideration of the original poisoning case.
