A hidden-camera video shows Berkeley chemical engineer David Xu secretly poisoning his co-worker’s water bottle. The footage, captured in 2019 by the victim, Rong Yuan, surfaced publicly after Xu successfully petitioned an Alameda County judge to expunge his felony conviction. [1, 3]
Case Background & The Video
• The Crime: David Xu and Rong Yuan were co-workers at Berkeley Engineering and Research. Starting around 2017, Yuan experienced severe, unexplained health problems that repeatedly sent her to the emergency room. [1, 2]
• The Discovery: After noticing a strange smell from her water bottle, Yuan installed a spy camera at her desk. The footage caught Xu tampering with her water. Laboratory testing revealed the bottle contained cadmium, a highly toxic heavy metal, at levels up to 3.5 million times the federal drinking water limit. [1, 2, 3]
• Family Impact: Yuan's parents also tested positive for cadmium poisoning because the toxic substance spread through shared water vessels at home. [3]
Controversial Plea Deal and Expungement
• The Initial Charges: Xu was arrested in March 2019 and initially faced charges of premeditated attempted murder and two felony counts of poisoning, which carried a maximum sentence of life in prison. [1, 2, 5]
• The Sentence: Under a plea agreement negotiated by former Alameda County District Attorney Pamela Price, Xu pleaded no contest to a single felony count of poisoning in September 2023. In March 2024, he was sentenced to two years of probation and served no prison time. [1, 5, 7]
• Expungement: On October 13, 2026, a California judge approved Xu's request to have his felony conviction expunged, despite formal objections from the District Attorney's office. [3]
Yuan publicly released the surveillance footage out of deep frustration with the justice system, expressing concern that future employers and co-workers will have no way of knowing about Xu's criminal history. [3, 5]
Reporting indicates that Xu never provided a clear motive for the poisoning, though Yuan noted he frequently restricted her from accessing certain laboratory spaces. [3]