California engineer filmed poisoning colleague's water

A chemical engineer in California, David Xu, has been caught on hidden camera allegedly poisoning a colleague. The footage shows him tampering with Rong Yuan’s water bottle using cadmium, a toxic heavy metal.

Xu, who works at Berkeley Engineering and Research, poisoned Yuan through her food and water for almost 18 months from 2017 to 2019. This information came from reports by The San Francisco Standard and the New York Post on Monday.

The footage, recorded by Yuan in 2019, appears to show Xu adding something to her water bottle. Lab tests later confirmed the presence of cadmium in the bottle.

Yuan shared her feelings after watching the footage for the first time. "My blood was frozen," she said. "I almost died. I experienced death so, so close so many times. I cannot let him go."

Starting in 2017, Yuan faced serious health issues, including severe vomiting that sometimes required emergency care. On November 27, 2018, she emailed her colleagues to say she was unwell and needed a sick day.

Xu replied, suggesting she work from home until she felt better. He even commented that there was no need for her to rush back to the office, saying, "I think BEAR is moldy," referring to their workplace.

The poisoning came to light in early 2019 when Yuan set up a hidden camera at her desk. The recordings reportedly showed Xu messing with her water bottle.

A lab report reviewed by The San Francisco Standard indicated that the cadmium levels in the bottle were up to 3.5 million times higher than the federal limit for drinking water.

Yuan’s parents also faced exposure after accidentally drinking the contaminated water. Her mother once noticed a sour taste and had even used the water to cook.

Xu was arrested in March 2019 on charges of attempted murder and poisoning. The case lingered for years until Xu accepted a plea deal in 2023. He pleaded no contest to one felony count of poisoning in September that year, while the attempted murder charges were dropped.

In March 2024, he received a sentence of two years probation and was credited with one day spent in jail, according to reports.

Yuan sought close to $500,000 in restitution for the damage done to her and her family. However, Xu was ordered to pay only $7,058.

He finished his probation in March 2026 and is now trying to get his felony conviction cleared under California’s expungement process.

The San Francisco Standard reported that California law lets eligible defendants who have completed their probation ask for their convictions to be dismissed.

Yuan mentioned that she still suffers from long-term health effects from the poisoning and can't work full-time. She also wrote a research paper about the lasting health issues faced by her and her parents, dedicating it to her father, who passed away from heart failure.