On Monday, October 12th, a former colleague who had previously poisoned a water cup and had his record of a serious crime overturned faced public scrutiny for the first time. Rong Yuan, a Chinese woman in the Bay Area who was the victim, expressed her doubts about the decision to expunge David Xu’s record, despite the opposition from the prosecution, a California judge approved the application to overturn his conviction.
Yuan attended the hearing for the expungement of Xu’s record that day and after the decision, she voiced her concerns. She said, “I don’t believe he deserves a second chance. A second chance will allow him to continue to harm others and make more victims.”
Since 2017, Yuan has been dealing with a series of unexplainable health issues, including vomiting and hair loss. For years, she tried to figure out the cause. Eventually, she used a hidden camera and captured a shocking video showing Xu secretly poisoning her water cup.
Xu started working at Berkeley Engineering and Research in 2009. In January 2017, Yuan joined the same company. Both were mentored by materials scientist Robert Ritchie at the University of California, Berkeley, and obtained their doctoral degrees.
Between 2017 and 2019, Xu repeatedly put cadmium, a heavy metal, into Yuan’s drinking water cup. Tests showed positive cadmium poisoning results for Yuan and her parents, with concentrations up to 3.5 million times the federal drinking water standards. Yuan’s mother even used water from her cup to cook.
On March 28, 2019, the Alameda County District Attorney’s Office charged Xu with attempted premeditated murder and two counts of felony poisoning.
With the election of a new district attorney, Pamela Price, the poisoning case was delayed and disappeared from the public eye.
In September 2023, a plea agreement was reached, with Xu admitting to poisoning and the prosecution agreeing to a one-year probation as punishment.
During the sentencing hearing for Xu in March 2024, the judge was shocked by the leniency of the agreement, stating, “Considering all the circumstances of this case, this agreement is overly generous.”
The probation period for Xu was doubled to two years by the judge, with credit for time served.
In November 2024, Price was successfully recalled by voters, making it the first successful recall of a district attorney in the county’s history. She left office in December of the same year.
In September 2025, Xu completed his probation period.
On October 12, 2026, Xu applied to have his felony conviction record expunged at Alameda County Court. This process is commonly known as “expungement.”
Under California law, if Xu fulfills all conditions during probation, the judge must approve the expungement of the felony conviction record.
The district attorney’s office opposed Xu’s application to have his conviction record expunged.
Outside the courtroom, when asked by the media what she would like to say to Xu, Yuan replied, “Why would I talk to him? He’s a coward.”
“Poisoning is not something that can happen in a moment of loss of control; it was premeditated,” Yuan added.
She still doesn’t understand why Xu targeted her. She recalled that Xu had advised her to find another path and not work in the same lab.
The atmosphere was tense when Yuan first interacted with Xu at the company: Xu warned her not to use materials from the lab.
Court documents revealed that Xu was considered the third in line to take over as the chief senior engineer after the retirement of the previous engineer. He was concerned about Yuan competing for that position.
Yuan expressed guilt for bringing the poisoned water back home, leading to her family being affected.
“If I hadn’t brought my parents to the U.S., they wouldn’t have been poisoned. If I hadn’t brought the water cup home, they wouldn’t have been poisoned either,” Yuan said.
Her father passed away in 2025 due to heart failure.
Yuan stated that she decided to make this matter public partly because of her father’s passing.
“Stepping out of my comfort zone, giving interviews, and telling the public about the impact on my family and the flaws in this system,” she said.
Despite nearly a decade passing, Yuan mentioned that the health issues caused by the poisoning still persist, and she can only work part-time currently.
She published a research paper recently titled “Familial Oral Cadmium Sulfate Poisoning: A case series with seven-year multi-system follow-up,” exploring the long-term health consequences suffered by her and her parents due to cadmium poisoning.
The core finding of the paper was that “blood cadmium levels do not steadily decrease after a temporary increase but fluctuate over time as cadmium stored in the liver is gradually released into the body.”
Yuan hopes that this research can help doctors identify signs of cadmium poisoning earlier and make timely diagnoses.
“This way, tragedies like this won’t happen again,” she said.