A California judge on Monday cleared the felony conviction of a former materials engineer who poisoned his co-worker’s drinking water with toxic cadmium, prompting the victim to release desk surveillance footage of the crime as she criticized the legal system.
David Xu, a former senior engineer at Berkeley Engineering and Research, petitioned Alameda County Superior Court for the dismissal after completing two years of probation in March, according to court documents cited by local news organizations. Despite objections from prosecutors, the judge granted the expungement on Oct. 12 under California rules that allow defendants who fulfill probation terms to seek post-conviction relief.
Years of unexplained illness
The victim, Rong Yuan, began working alongside Xu in January 2017. Within months, she began suffering from unexplained health problems, including severe nausea, dry heaving and hair loss, she told ABC7 Bay Area and The San Francisco Standard. Repeated hospital visits failed to reveal a clear medical diagnosis as her condition deteriorated.
Suspicion arose in late 2018 and early 2019 when Yuan and her family detected unusual odors and sour tastes in water she brought home from her desk. Both of her parents subsequently fell ill. After cleaning the container did not eliminate the odd odor, Yuan purchased a small camera online and positioned it at her workstation in February 2019.
The hidden camera captured Xu tampering with her desk area on Feb. 11, 2019, and footage recorded on March 4 showed him opening her bottle and pouring in an unknown substance, according to police records. Yuan handed the footage and water samples to the Berkeley Police Department.
Laboratory analysis later found cadmium concentrations roughly 3.5 million times above the federal threshold for drinking water, according to laboratory reports reviewed by local media. Yuan and both of her parents tested positive for heavy-metal poisoning.
Plea deal and sentencing
Police arrested Xu at his Lafayette home in late March 2019, initially booking him on suspicion of premeditated attempted murder alongside two felony poisoning counts. In September 2023, he accepted a plea agreement with the Alameda County District Attorney’s Office, pleading no contest to a single felony count of poisoning while prosecutors dismissed the remaining charges.
During a March 2024 sentencing hearing, Superior Court Judge Kimberly Colwell called the prosecution agreement “extremely generous,” the San Francisco Chronicle reported. The judge lengthened the proposed one-year probation term to two years and warned Xu never to touch poison again. Xu served 10 days in jail early in the case and was placed on electronic monitoring before finishing his formal probation.
Under California statute, dismissals granted after probation typically remove convictions from routine employment screenings, though law enforcement agencies and state licensing boards can still view the underlying criminal record, according to Yahoo News.
Victim speaks out after ruling
Yuan told ABC7 Bay Area that she decided to speak publicly and release the video because she believes the justice system failed to protect her or hold Xu accountable. She reported that although she sought $500,000 in restitution, she received $7,000.
“I don’t think he deserves a second chance. A second chance for a lot to hurt other people, to make other people turning into victims,” Yuan told the station.
Yuan said she continues to deal with long-term medical complications that leave her able to work only part time. Her father died of heart failure last year, an event she said influenced her decision to tell her story publicly.
It remains unclear why Xu targeted Yuan, as prosecutors and court records have not established a motive, and Xu has never publicly explained his actions.
