Engineer Caught on Camera Poisoning Coworker Gets Felony Conviction Dismissed

A California engineer caught on hidden camera poisoning his coworker's water with a toxic heavy metal has had his felony conviction dismissed after receiving two years of probation instead of a potential life sentence. An Alameda County Superior Court judge granted David Xu's request on October 12, 2026, despite objections from prosecutors and the victim, Rong Yuan, who says the poisoning left her with lasting health problems.

Judge Pelayo Llamas approved the dismissal after Xu completed probation under a 2023 plea agreement that dropped charges of premeditated attempted murder and a second poisoning offense. California law generally requires courts to dismiss qualifying convictions once defendants satisfy their probation conditions, leaving judges little discretion when those requirements are met.

Xu and Yuan worked at Berkeley Engineering and Research, where prosecutors said he repeatedly contaminated her food and drinking water with cadmium, a carcinogenic heavy metal, between 2017 and 2019.

Yuan began experiencing unexplained illnesses in 2017, including severe vomiting, chronic nausea and hair loss. Her symptoms repeatedly sent her to the hospital as doctors struggled to identify the cause. She eventually grew suspicious after her mother noticed an unusual taste and odor in water kept at her workplace.

In March 2019, Yuan installed a concealed camera near her desk. Footage recorded on March 4 showed Xu entering her office, pouring a substance into her water bottle, replacing the cap and walking away. She released the video publicly in October 2026 as she sought to prevent his conviction from being dismissed.

Laboratory testing subsequently found cadmium concentrations approximately 3.5 million times the federal drinking water limit in one sample. Yuan and her parents, who had consumed contaminated water she brought home, also tested positive for elevated levels of the toxic metal, which can damage the kidneys and other organs.

Berkeley police arrested Xu on March 28, 2019, and prosecutors charged him with premeditated attempted murder and two felony counts of poisoning, along with allegations involving great bodily injury. The most serious charge carried a potential life sentence.

The case continued for more than four years before Xu accepted a plea agreement in September 2023. He pleaded no contest to one felony poisoning count, carrying the same effect as a guilty plea in the criminal case. Prosecutors dismissed the attempted murder charge and the remaining poisoning count.

At his sentencing in March 2024, Alameda County Superior Court Judge Kimberly Colwell described the agreement as "extremely generous, considering everything in this case." She increased the proposed probation period from one year to two years and ordered Xu to stay away from Yuan and her parents.

Xu received credit for one day of jail confinement at sentencing. He had also spent several days in custody following his 2019 arrest before posting $2 million bail and securing release under GPS monitoring. The plea agreement allowed him to avoid additional jail time.

After completing probation in March 2026, Xu filed a petition in July to dismiss his conviction under California Penal Code Section 1203.4. The statute generally entitles eligible defendants who fulfill their probation conditions to withdraw a guilty or no-contest plea and have their charges dismissed, even when prosecutors or victims oppose the request.

At the October 12 hearing, Yuan delivered a victim impact statement before Judge Llamas, while Assistant District Attorney Priscilla Vuong opposed Xu's petition. The court granted the dismissal, and Alameda County District Attorney Ursula Jones Dickson subsequently confirmed that prosecutors had challenged the motion.

Yuan described continuing health complications that have affected her ability to work full time, along with the toll the poisoning has taken on her family. Her parents also suffered health problems after consuming contaminated water, and her father died of heart failure in 2025. Yuan believes the exposure contributed to his declining health and death, although a direct medical connection has not been established.

Her opposition also reflected concerns about Xu's future employment. The dismissal generally prevents covered private employers from considering the conviction in hiring decisions under California law, though the criminal history remains accessible through certain official records. Disclosure is still required for specified government positions, professional licenses, and other exceptions.

Yuan criticized the legal framework that allowed Xu to obtain relief despite the seriousness of his original charges, while acknowledging that Judge Llamas was applying the law governing probation-related dismissals.

"The judge has to grant the petition according to the current law. I never blame the judge," Yuan said after the hearing.