Surveillance footage appears to show a California engineer contaminating his colleague’s water bottle with cadmium, after she endured nearly two years of unexplained illness. David Xu, a metallurgist at Berkeley Engineering and Research, is now seeking to have his felony conviction dismissed after completing a two-year probation sentence.
Rong Yuan, 50, suffered repeated bouts of vomiting, hair loss and dry heaving between 2017 and 2019. She was hospitalised several times, feared she had stomach cancer and travelled to China for medical treatment, but doctors initially failed to identify the cause.
Xu, who had faced a charge of premeditated attempted murder, ultimately pleaded no contest to one felony count of poisoning. He received two years’ probation and credit for one day spent in custody.
Yuan says she remains in poor health and cannot work full-time. She is now opposing Xu’s application to have the conviction dismissed, fearing the move could make it harder for future employers to discover what happened.
Hidden camera records suspected poisoning
The footage was recorded after Yuan became convinced that someone was tampering with her food and drink. She bought a hidden camera and installed it near her desk.
In a recording dated February 11, 2019, Xu can be seen approaching the desk and reaching towards the area where her water bottle was kept. A second video, recorded on March 4, shows him pouring a substance from a small white container into the bottle before returning roughly 30 seconds later and rotating it.
Yuan’s mother had noticed an unusual sour taste in the bottle’s water in January 2019. Police later found what the source material describes as massive concentrations of cadmium in the drink.
Laboratory testing reportedly found levels 3.5 million times higher than the federal drinking-water limit. Blood samples from Yuan and both her parents also tested positive for cadmium after her mother had unknowingly used water from the bottle to prepare family meals.
Berkeley Police Sergeant Jennifer Wilson said the recordings were crucial to the investigation.
“It was shocking,” she said. “No one would have believed her in the world that this was happening if she didn’t have proof of it. … It really launched this case immediately.”
Yuan said she was overwhelmed when she first watched the footage.
“My blood was frozen,” she said. “I almost died. I experienced death so, so close so many times. I cannot let him go.”
Illness began after joining engineering company
Yuan joined Berkeley Engineering and Research, a forensic engineering company, in January 2017. She and Xu had both earned doctorates through the University of California, Berkeley, and specialised in metals.
She recalled an uncomfortable early encounter in which Xu told her she could not use the company’s materials characterisation laboratory. Yuan said she chose to avoid a confrontation and keep her distance.
Within weeks, she began experiencing symptoms including hair loss and dry heaving. In July 2017, she became severely ill after drinking from her water bottle and was taken to an emergency department by a neighbour.
As the episodes continued, Xu appeared to present himself as a concerned colleague. When Yuan emailed co-workers in November 2018 to say that she was vomiting again, he replied: “You should work from home until you feel better. No reason to rush in.”
He also suggested that the company’s office might be responsible, writing: “I think BEAR is moldy.”
Yuan’s parents travelled from China to help care for her. She later said that she had repeatedly feared she was dying, while medical examinations failed to explain her condition.
Xu seeks dismissal of conviction
Xu was charged in March 2019 with premeditated attempted murder and two felony poisoning offences. He was released on two million dollars bail and placed under GPS monitoring, although restrictions on his movements were later eased.
In September 2023, prosecutors offered a plea agreement that removed the attempted murder charge. Xu pleaded no contest to a felony poisoning count, a plea that has the legal effect of a conviction without an admission of the underlying allegations.
At his sentencing in March 2024, Judge Kimberly Colwell described the agreement as “extremely generous, considering everything in this case” and extended the proposed one-year probation term to two years. She also ordered Xu to stay away from Yuan and her parents.
“Please do not touch any poison at all. Ever. Ever,” the judge warned.
Yuan sought almost 500,000 dollars in restitution but was awarded 7,058 dollars. The court considered a defence toxicologist’s report disputing whether cadmium poisoning would cause long-term health effects, conclusions Yuan strongly contests.
Xu completed probation in March 2026 and is asking an Alameda County judge to dismiss the conviction under California’s record-dismissal law.
“This legal system already failed me,” Yuan said. “This is my last resort.”
