When news broke that a chemical engineer in California had been caught poisoning his coworker, people were horrified. Surveillance footage surfaced, slightly grainy but clear enough, showing David Xu sneaking over repeatedly to tamper with Rong Yuan’s water bottle. The case exploded, not just because of the chilling behavior but because of how long Yuan suffered before anyone realized what was happening.Years went by as she battled strange, relentless illnesses that doctors couldn’t explain. Her health kept spiraling. Hospital visits blurred together with tests and desperate searches for answers. Hidden cameras finally helped uncover the truth, but even after Xu was convicted, the story wasn’t over.Now, as Xu tries to erase his conviction, fresh questions have surfaced: what does justice look like in cases like these? Why did the punishment feel so light? How safe are our workplaces, really?
Who is Rong Yuan, and what happened to her?
Let’s rewind. According to The San Francisco Standard, back in 2017, Yuan, an engineer, started working at Berkeley Engineering and Research, which is a forensic firm in the Bay Area. Not long after, her health went sideways. At first, it was mild: dry heaving, hair falling out. But things escalated. She was vomiting all the time, everything tasted sour, and she ended up in the ER more than once. She tried everything, even flying to China to see specialists. For a while, she thought she might have cancer. But the tests and scans kept coming back inconclusive.Things changed when Yuan’s parents flew in from China, hoping to help. Her mother drank from Yuan’s water bottle and detected a weird, sour note. Yuan, already suspicious, started wondering if someone could be poisoning her. Gut feeling turned to determination. She started investigating herself, since doctors had run out of options.By early 2019, she’d had enough. Yuan bought a tiny surveillance camera and planted it on her desk. What she recorded was shocking. On February 11, Xu was caught on film approaching Yuan’s desk and fiddling with her water bottle. On March 4, he returned with a small white container, poured something into the bottle, rotated it, and walked away. Watching this footage, Yuan realized her fears were real. She gave the evidence to police.Tests ran soon after showed her water bottles were loaded with cadmium: up to 3.5 million times the federal safety limit. When police tested blood samples from Yuan and her parents, the results showed cadmium poisoning across the board. Her mother had used that water for cooking, so the whole family was exposed. Berkeley police moved fast, arresting Xu in March. He faced charges for attempted murder and felony poisoning.
Cadmium: What is it, and why is it so deadly?
For the unversed, Cadmium is a heavy metal found in batteries, some paints, industrial materials, and it’s surprisingly easy to get if you know where to look. Exposure can wreck your kidneys, lungs, and bones. It’s a recognized cancer risk. In Yuan’s case, this was slow-motion poisoning, not a single event: she endured toxic exposure for months, maybe years. After surviving, she’s still grappling with health problems, and she can’t work full-time. Her story shows how hidden, gradual poisoning can be terrifyingly hard to diagnose or even suspect.
What happened to David Xu?
Now, Xu’s sentencing has become another point of attention. At first, prosecutors charged him with attempted murder, but he struck a plea deal and pleaded “no contest” to felony poisoning. This plea isn’t exactly admitting guilt but has the same legal weight. Xu ended up with probation (yes, two years, not prison time) and credit for one day in jail. The restitution was shockingly low: about $7,058, compared to the nearly half a million Yuan requested. The court leaned on a toxicologist’s report that claimed long-term effects from cadmium poisoning wouldn’t be expected, but Yuan disagrees, as her suffering is real and ongoing. To many, the sentence felt insultingly light for what happened.Xu finished his probation in March 2026. Now he wants to clear his record entirely, using California’s expungement process. The Alameda County DA opposes this, but the law’s on Xu’s side if he meets all the requirements.
What’s next?
As of now, Yuan has become a voice for others. She released the surveillance footage and has been vocal about her lasting health issues, hoping the attention will help other victims get diagnosed sooner. Cadmium poisoning, she says, shouldn’t be overlooked or misunderstood.Underneath the drama, the case is really about more than just a disturbing workplace crime. And the question that keeps coming back: Should the punishment fit the crime if the crime itself is nearly invisible and the suffering lasts a lifetime? Can the legal system really account for that kind of pain?