Watch: Chilling Spy-Cam Video Catches Engineer Poisoning Colleague With Cadmium Over 18 Months

Newly released spy-camera footage appears to show chemical engineer David Xu pouring a substance into his co-worker Rong Yuan's water bottle at a California engineering firm.

Police records cited by The San Francisco Standard say Xu put cadmium in Yuan's food and water on multiple occasions over more than a year, while laboratory testing found cadmium levels in her water bottle up to 3.5 million times the US federal drinking-water limit.

Xu, who worked at Berkeley Engineering and Research, was arrested in 2019 and later pleaded no contest to one felony count of poisoning in September 2023. The footage was recorded in 2019, after Yuan had spent nearly two years suffering unexplained health problems that began in 2017.

On 12 October 2026, a judge granted Xu's request to have his felony conviction expunged, despite objections from prosecutors.

Spy-Camera Footage Exposes Workplace Poisoning

Yuan spent years searching for answers to a series of mysterious health issues that began in 2017, including hair loss and severe vomiting, before discovering what she says was happening at her office.

When asked how she felt after reviewing her own surveillance footage, Yuan said, 'Shocked. I don't know why.'

For nearly two years, her condition worsened as doctor after doctor failed to pinpoint the cause. Everything changed when her mother noticed a strange smell coming from Yuan's water bottle. Washing it made no difference, prompting Yuan to install a hidden camera at her desk.

'I never expected that I can capture anybody. It's a just an engineer's routine. If you have some issue, you think about the root cause,' Yuan recalled.

The footage captured Xu pouring an unidentified substance from a small container into Yuan's water bottle. According to The San Francisco Standard, a Berkeley Police Department report stated that Xu had put cadmium into Yuan's food and water on multiple occasions for more than a year. Laboratory testing subsequently confirmed cadmium in samples from her water bottle.

Water Sample Reveals Toxic Cadmium Levels

According to an ABC7 Eyewitness News report citing laboratory findings, a water sample from Yuan's bottle contained cadmium concentrations 3.5 million times higher than the US federal drinking-water limit.

The impact extended beyond Yuan. Blood tests found cadmium in Yuan and both her parents, according to The San Francisco Standard and ABC7. Yuan believes her family was exposed after water from the contaminated bottle was brought home and used in cooking.

Prosecutors charged Xu with premeditated attempted murder and two felony counts of poisoning in 2019. He faced the possibility of life in prison but ultimately accepted a plea deal.

In September 2023, Xu pleaded no contest to one felony count of poisoning. A no-contest plea carries the same legal weight as a conviction but is not an admission of the underlying facts. At his sentencing in March 2024, the judge increased the proposed one-year probation period to two years. Xu also received credit for one day served in jail.

Yuan has strongly criticised the outcome and fears that clearing Xu's conviction could make it harder for future employers to discover his criminal history.

'I don't think he deserves a second chance. A second chance for a lot to hurt other people, to make other people turning into victims,' Yuan said.

Judge Grants Xu's Request to Expunge Conviction

On 12 October 2026, a judge granted Xu's request to have his felony poisoning conviction expunged, despite objections from prosecutors.

However, the ruling does not mean the case or the underlying conviction simply disappears from every record. According to The San Francisco Standard, the arrest and conviction would still appear on Xu's record, and the conviction could be used against him if he were charged with another crime. He would also have to disclose it when applying for state licences.

The ruling has renewed Yuan's concerns about the justice system and the possibility that Xu's conviction may be less visible to prospective employers.

Yuan said she still does not know why Xu targeted her. She recalled instances when he discouraged her from working in the lab and suggested that she look for opportunities elsewhere.

'Why do I talk to him? He's a nobody. He's a coward,' she remarked when asked what she would say to him today. 'Poisoning is not something like you suddenly got angry and lose control. It's planned.'

Poisoning Devastated Yuan's Family

Yuan said the fallout extended far beyond her own health, leaving her feeling guilty about inadvertently bringing contaminated water into her home.

'If I don't ask you to come to the U.S., they will be poisoned. If I don't bring the water back home, they won't be poisoned,' Yuan said.

Her father died from heart failure last year. Yuan said his memory was a driving force behind her decision to speak publicly about the case.

'To come out of my comfort zone, to be interviewed about you, to tell the public what kind of effect it had on my family and how broken the system is,' she explained.

Yuan has described the wider toll she believes the poisoning took on her family. However, her father's death was attributed to heart failure, and the available reporting does not establish that cadmium exposure caused his death.

Ongoing Health Issues and $7,058 Payout

Nearly a decade after her health problems began, Yuan says she continues to experience complications following more than a year of chemical exposure and is now able to work only part-time.

She sought nearly $500,000 (£378075) in restitution to cover her damages, but the court ordered Xu to pay $7,058 (£5336.91).

The San Francisco Standard reported that the judge cited a report submitted by Xu's defence, written by a toxicologist who concluded that cadmium poisoning would not cause long-term health effects.

Yuan disputed the report's scientific conclusions. The toxicologist's assessment was the defence expert's position, not an independently established finding that cadmium exposure could not have lasting effects.

The disparity between the amount Yuan sought and the award adds to her frustration with the outcome of the criminal case.

Although she continues to deal with the physical effects she attributes to the poisoning, Yuan says she has little choice but to move forward while questioning the justice system's decision to dismiss Xu's felony conviction.