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US engineer caught on camera poisoning colleague’s water bottle

By Linda Ikeji 12 October 2026, 11:00 pm 0 comments

A California engineer convicted of poisoning a colleague is seeking dismissal of his felony conviction after completing probation, as the woman releases surveillance footage she says exposed the attacks. David Xu, 41, a metallurgist at Berkeley Engineering and Research, pleaded no contest to one felony poisoning count in September 2023 after prosecutors dropped a charge of premeditated attempted murder.

His former colleague, Rong Yuan, 50, told the San Francisco Standard that she released the recordings because she continued to suffer serious health problems and believed the legal process had failed her. “This legal system already failed me,” she said. “This is my last resort.” Yuan said she experienced repeated bouts of vomiting, hair loss and other unexplained symptoms between 2017 and 2019, leading to hospital admissions and consultations with specialists.

The problems began shortly after she joined the forensic engineering company in January 2017. Both she and Xu had earned doctorates at the University of California, Berkeley, and specialised in metals. Yuan recalled an early disagreement in which Xu told her she could not use the company’s materials characterisation laboratory. “I know how to use all these tools,” she recalled telling him. “I’ve even repaired them.”

She said she subsequently tried to avoid confrontation and concentrate on her work. By July 2017, her symptoms had worsened. After drinking from her water bottle one morning, she became severely ill and a neighbour took her to an emergency department. “I began to feel like I was dying,” she said.

Further episodes prompted additional hospital visits and a trip to China for medical treatment, but examinations did not explain her condition. Her parents later travelled from China to help care for her. When Yuan emailed colleagues on November 27, 2018, describing another episode of vomiting, Xu suggested that conditions in the office might be responsible. “You should work from home until you feel better. No reason to rush in,” he wrote. “I think BEAR is moldy.”

In January 2019, Yuan’s mother noticed an unusual sour taste after drinking from her daughter’s bottle. Suspecting deliberate contamination, Yuan installed a hidden camera. A recording dated February 11, 2019, reportedly shows Xu approaching her desk and reaching towards the area where the bottle was kept.

Another recording, from March 4, shows him pouring a substance from a small white container into the bottle before returning about 30 seconds later to rotate it. “My blood was frozen,” Yuan said of watching the footage. “I almost died. I experienced death so, so close so many times. I cannot let him go.”

According to a laboratory report reviewed by the Standard, water from the bottle contained cadmium at concentrations reaching 3.5 million times the federal drinking-water limit. Blood samples from Yuan and both her parents also tested positive for the metal. Her mother had unknowingly used water from the contaminated bottle to prepare family meals. Berkeley Police Sergeant Jennifer Wilson, who investigated the case, said the footage provided crucial evidence.

“It was shocking,” Wilson 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.” Xu was charged in March 2019 with premeditated attempted murder and two felony poisoning offences. He was later released on $2 million bail with GPS monitoring.

Prosecutors offered a plea agreement in September 2023 that dropped the attempted murder charge. Xu pleaded no contest to one poisoning count. At sentencing in March 2024, Judge Kimberly Colwell described the proposed one-year probation term as “extremely generous, considering everything in this case” and increased it to two years.

Xu received credit for one day spent in custody and was ordered to stay away from Yuan and her parents. “Please do not touch any poison at all. Ever. Ever,” the judge told him. Yuan sought almost $500,000 in restitution but was awarded $7,058 after the court considered a defence toxicologist’s report disputing whether the poisoning would cause long-term health effects. She contests those conclusions.

Xu completed probation in March 2026 and is seeking relief under California’s record-dismissal law. A successful petition would not erase the conviction from law-enforcement records, but Yuan fears it could make the case harder for future employers to discover. She said her health remained impaired and she was unable to work full time.

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