Engineer Caught on Camera Poisoning Colleague with Cadmium

A metallurgist at Berkeley Engineering and Research, David Xu, has been exposed by hidden camera footage for systematically poisoning his female colleague's water bottle with cadmium between 2017 and 2019. The colleague, Rong Yuan, suffered nearly two years of debilitating and mysterious illnesses, including uncontrollable vomiting and hospitalization, before she installed a hidden camera to catch her assailant.

Initially facing attempted murder charges, Xu, 41, pleaded no contest to a single felony count of poisoning. He was sentenced to two years of probation and received credit for one day served. He is now seeking to have his conviction dismissed under California's record-dismissal law, a move that has angered Yuan, who continues to experience health problems.

Yuan, who specialized in metals and had earned a doctorate from the University of California, Berkeley, joined the company in January 2017. Shortly after her arrival, she began experiencing symptoms like hair loss and dry heaving. By July 2017, her condition worsened significantly after drinking from her water bottle, leading to a neighbor rushing her to the emergency room.

Despite numerous medical consultations and even travel to China for treatment, doctors could not diagnose her condition. The breakthrough came in January 2019 when Yuan's mother noticed a peculiar taste in her water. Suspecting foul play, Yuan purchased a hidden camera, which captured Xu tampering with her water bottle on multiple occasions. Surveillance footage shows Xu approaching her desk, pouring a substance from a small white container into her bottle, and then returning to rotate it.

Police investigations revealed extremely high concentrations of cadmium in Yuan's water, millions of times the federal drinking-water limit. Blood tests also confirmed the presence of cadmium in Yuan and her parents, who had unknowingly consumed the contaminated water.

Berkeley Police Sergeant Jennifer Wilson described the surveillance footage as crucial, stating that "No one would have believed her in the world that this was happening if she didn't have proof of it." Xu was arrested in March 2019.

In September 2023, prosecutors offered Xu a plea agreement that dropped the attempted murder charge. He pleaded no contest to the poisoning charge, a plea that legally functions as a conviction without admitting guilt. At his sentencing in March 2024, Judge Kimberly Colwell deemed the plea arrangement "extremely generous" and increased the probation to two years, also ordering Xu to stay away from Yuan and her parents.

Yuan sought nearly $500,000 in restitution but was awarded only $7,058. She disputes a defense toxicologist's report that claimed cadmium poisoning would not cause long-term health effects. Xu completed his probation in March 2026, and if his conviction is dismissed, it would not erase it from law enforcement records but could prevent future employers from discovering the details of the case. Yuan maintains that her health remains compromised, preventing her from working full-time.