A California engineer who was caught on a hidden camera pouring a substance into his co-worker’s water bottle is asking a judge to dismiss his felony poisoning conviction, years after the victim endured a mysterious illness that repeatedly sent her to the hospital.
The surveillance footage, recorded in 2019 at Berkeley Engineering and Research, was released publicly this weekend by the victim, Rong Yuan. It shows her former colleague, David Xu, approaching her desk and tampering with the bottle while she was away.
Xu initially faced charges that could have resulted in life in prison. Instead, he pleaded no contest to one felony poisoning count and received probation. Now, after completing that sentence, he is seeking a dismissal that could remove the conviction from many routine employment background checks.
Yuan, who says she continues to suffer health problems from the poisoning, is speaking publicly about the case as Xu prepares to appear in Alameda County Superior Court on Monday, October 12. She fears the legal system is about to give him another opportunity to move beyond a crime that changed her life.
The Hidden Camera
Embedded media follows; please allow a moment to load.
Yuan began working at Berkeley Engineering and Research in 2017. Within months, she started experiencing unexplained symptoms, including nausea, vomiting and hair loss. Her condition deteriorated as she sought answers from doctors and repeatedly visited hospitals.
She eventually noticed something strange about the food and water she left unattended at work. Her water sometimes had an unusual taste, and her parents also became sick after consuming water she had brought home.
According to police records documented by Berkeleyside in 2019, those suspicions ultimately led Yuan to install a surveillance camera near her desk.
On February 11, 2019, the camera captured Xu reaching toward the area where she kept her water bottle. A second recording on March 4 provided a clearer view.
Xu entered her workspace, unscrewed the bottle and poured a substance from a small container into the water. He then returned and adjusted the bottle’s position before leaving.
The newly public footage captures the encounter that helped expose what had been happening.
“My blood was frozen,” Yuan recalled in an interview with The San Francisco Standard, describing her reaction to seeing the recording.
Inside The Bottle
Yuan turned the recordings and water samples over to Berkeley police. Laboratory testing revealed extraordinarily high concentrations of cadmium, a toxic heavy metal.
One sample contained cadmium at levels reaching approximately 3.5 million times the federal drinking-water limit, according to a laboratory report reviewed by The Standard.
Blood tests also showed elevated cadmium levels in Yuan and both her parents.
Cadmium exposure can cause serious health problems. The Agency for Toxic Substances and Disease Registry warns that consuming high concentrations can cause severe gastrointestinal symptoms and potentially death. Prolonged exposure can damage the kidneys and weaken bones.
Berkeley police arrested Xu at his Lafayette home on March 28, 2019. Prosecutors charged him with premeditated attempted murder and two felony poisoning counts.
The criminal case would take years to resolve.
A Different Outcome
In September 2023, Xu pleaded no contest to a single felony poisoning count under an agreement with the Alameda County District Attorney’s Office. The attempted-murder charge and another poisoning count were dismissed.
When Xu returned for sentencing in March 2024, Judge Kimberly Colwell expressed concern about the unusually favorable terms.
The judge described the sentence as “extremely generous,” according to a San Francisco Chronicle review of the sentencing transcript.
The agreement originally called for one year of probation. Colwell increased that to two years.
“Please do not touch any poison at all,” she told Xu during sentencing. “Ever. Ever.”
Despite the seriousness of the original charges, he received probation rather than a state prison sentence.
The Berkeley Scanner’s examination of court records found that Xu had served 10 days in jail early in the proceedings and spent part of the following years under electronic monitoring.
Back Before A Judge
Xu completed his probation in March 2026. He is scheduled to appear in Alameda County Superior Court at 9 a.m. Monday, October 12, seeking dismissal of the felony conviction.
Under California law, people who successfully complete probation may qualify to have qualifying convictions dismissed. Although commonly described as expungement, the process does not completely erase the criminal case. Certain government agencies and licensing authorities can still access the record.
Court records reviewed by The Standard indicate that the district attorney’s office is opposing Xu’s petition. The judge has not yet ruled on the request.
Yuan says the consequences of the poisoning have continued long after Xu completed his sentence. She reports ongoing health problems that prevent her from working full time.
She also fears that dismissal could make it easier for Xu to conceal his conviction from future employers.
“This legal system already failed me,” Yuan told The Standard. “This is my last resort.”
Yuan plans to attend Monday’s hearing, where she has the right to address the court before it decides whether to grant Xu’s request.