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A California engineer who was filmed tampering with a colleague's water bottle is seeking dismissal of his felony poisoning conviction after completing probation. The request revives a case in which hidden-camera footage exposed alleged cadmium poisoning over nearly 18 months.
The poisoning came to light in early 2019, when Yuan installed a hidden camera at her desk. (Screen grabs: X/Berkeley Police Department)
Oct 12, 2026 10:17 IST
A California chemical engineer who secretly poisoned a colleague with a toxic heavy metal for nearly 18 months is seeking to have his felony conviction dismissed after completing probation, despite video evidence showing him tampering with her water bottle. David Xu, a metallurgist at Berkeley Engineering and Research (BEAR), pleaded no contest to a felony poisoning charge after his colleague Rong Yuan suffered severe health problems, reported the New York Post.
Xu allegedly spiked Yuan’s food and drinking water with cadmium, a known toxic metal, between 2017 and 2019. As Yuan experienced debilitating symptoms and made repeated hospital visits, she feared she could be suffering from a potentially fatal illness.
The poisoning came to light in early 2019, when Yuan installed a hidden camera at her desk. The footage captured Xu tampering with her water bottle, providing crucial evidence in the case.
“My blood was frozen,” Yuan told The San Francisco Standard, recalling her reaction to watching the footage for the first time. “I almost died. I experienced death so, so close so many times. I cannot let him go,” she was quoted as saying.
COLLEAGUE BLAMED OFFICE MOULD FOR HER ILLNESS
As Yuan’s health deteriorated, Xu allegedly maintained a facade of concern while suggesting that mould in the workplace could be responsible for her illness.
On November 27, 2018, Yuan emailed colleagues to say she was suffering from severe vomiting and needed to take a sick day. Xu responded by advising her to work from home until she felt better.
“You should work from home until you feel better. No reason to rush in,” he wrote, adding, “I think BEAR is moldy,” according to The San Francisco Standard.
The poisoning was uncovered only after Yuan decided to monitor her desk with a concealed camera. The footage showed Xu tampering with her water bottle, prompting an investigation into the suspected poisoning.
ARRESTED IN 2019, ATTEMPTED MURDER CHARGES DROPPED
Xu was arrested in March 2019 on charges of attempted murder and poisoning. The case also involved Yuan’s parents, who had inadvertently consumed the contaminated water, according to reports.
Following his arrest, Xu was released on USD 2 million bail. His home-confinement conditions were subsequently modified several times, and his travel restrictions were eventually lifted, The San Francisco Standard reported.
In late 2023, Xu reached a plea agreement with then-Alameda County District Attorney. The attempted murder charges were dropped, and he pleaded no contest to a single felony count of poisoning.
He was sentenced to two years of probation and received credit for one day spent in custody.
SEEKS DISMISSAL OF FELONY CONVICTION
Yuan had sought nearly USD 500,000 in restitution for the harm she suffered. However, the court ordered Xu to pay USD 7,058 in restitution.
Xu completed his probation in March 2026 and is now seeking to have his felony conviction formally dismissed under California’s expungement law.
Under California law, defendants who meet the statutory requirements, including completing their probation, may qualify to have their convictions dismissed. Such a dismissal does not mean that the underlying conduct never occurred, nor does it necessarily erase the conviction from every record.
The request comes years after the poisoning was exposed through Yuan’s hidden-camera footage and the attempted murder charges were dropped as part of the plea agreement.
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