David Xu

Introduction

David Xu is a Lafayette, California metallurgist and chemical engineer who poisoned his colleague Rong Yuan’s food and water with cadmium — a toxic heavy metal — on multiple occasions over nearly 18 months at the forensic engineering firm Berkeley Engineering and Research in Berkeley, a campaign that went undiagnosed for two years until Yuan hid a spy camera at her desk and caught him on video tampering with her water bottle. Charged in 2019 with premeditated attempted murder, Xu instead pleaded no contest to a single felony count of poisoning under a plea deal offered by then-Alameda County District Attorney Pamela Price, and was sentenced to probation with one day of credited custody. He completed probation in March 2026 and is now asking a judge to dismiss the conviction.

The New York Post carried the story as new surveillance video was released: “Berkeley engineer caught on video poisoning coworker before she suffered horrific health problems.”

Background Information

Xu received his undergraduate and graduate degrees from UC Berkeley, and at different times both he and Yuan earned doctorates in the UC Berkeley materials-science lab of Professor Robert Ritchie. He worked at Berkeley Engineering and Research (BEAR) — where he had worked since at least 2009 — as the firm’s sole materials characterization expert and head metallurgist, running its materials and metallurgy lab. In 2013 he was quoted widely in connection with the failure of seismic safety bolts on the San Francisco–Oakland Bay Bridge, and according to an earlier version of his resume he did testing connected to the 2010 San Bruno pipeline explosion and offered his services as an expert witness at $350 an hour.

The Controversy or Incident That Led to Their Cancellation

Convicted by plea — now petitioning to erase it. Xu pleaded no contest in 2023 to a single felony count of poisoning after attempted-murder charges carrying up to life in prison were dropped in a deal from DA Pamela Price’s office; a judge doubled his probation to two years and gave him one day of credit for time served. Having completed probation in March 2026, he is petitioning under California’s expungement statute to have the felony conviction formally dismissed. The poisoning facts were established by his own plea; his expungement petition is contested by the district attorney’s office.

Yuan, hired at BEAR in January 2017, began suffering dry heaving and hair loss within weeks, then regular vomiting, a persistent sour taste, and repeated emergency-room visits — she feared stomach cancer, flew to China for treatment, and tests found nothing. In November 2018 she emailed colleagues that she was severely vomiting and taking a sick day; Xu replied, “You should work from home until you feel better. No reason to rush in,” adding, “I think BEAR is moldy.” In January 2019, after Yuan’s mother drank from the bottle and noticed a sour taste, Yuan suspected tampering and bought a hidden camera. Footage from February 11, 2019 shows Xu at her desk reaching toward the bottle; a second video dated March 4 shows him pouring a substance from a small white container into it. She turned the evidence over to Berkeley police that day.

Sergeant Jennifer Wilson of Berkeley Police’s homicide unit called the video shocking: “No one would have believed her in the world that this was happening if she didn’t have proof of it.” Lab testing found cadmium in Yuan’s water bottle at levels up to 3.5 million times the federal drinking-water limit, and blood samples from Yuan and both her parents — her mother had cooked with water from the bottle — tested positive for elevated cadmium. On March 28, 2019, the Alameda County District Attorney charged Xu with premeditated attempted murder and two felony counts of poisoning. His attorney, Julia Jayne, called it “an isolated work-related incident”; a judge set bail at $2 million and Xu was released on GPS monitoring, after which the state AG — calling him “a highly trained and unusually sophisticated criminal defendant” — barred him from practicing under his engineering licenses while the case was pending. Over the following years the court granted repeated leniency: extra hours for his daughter’s activities, an end to house arrest in November 2021, and US travel by April 2022.

Public Reaction and Consequences

The plea deal drew statewide attention to DA Pamela Price, who was recalled by voters in 2024 partly over her lenient plea deals; the judge who sentenced Xu in March 2024, Kimberly Colwell, called the deal “extremely generous, considering everything in this case,” doubled the probation term, ordered Xu to stay away from Yuan and her parents, and admonished him: “Please do not touch any poison at all. Ever. Ever.” Yuan, who had never spoken publicly before, is now releasing the spy-cam videos herself: “My blood was frozen,” she said of first watching the footage. “I almost died. I experienced death so, so close so many times. I cannot let him go.” Of the expungement petition she said, “This legal system already failed me. This is my last resort.” Berkeley PD’s Wilson praised her persistence: “[Xu] never weakened her — even when she was so sick, she just kept fighting back.” BEAR did not respond to requests for comment.

Current Status

Xu completed his two years of probation in March 2026. On Monday, October 12, 2026, an Alameda County Superior Court judge in Department 109 will hear his petition to dismiss the felony conviction — a process California judges are effectively bound to grant for defendants who complete every probation condition, and poisoning is not on the short list of excluded crimes. The district attorney’s office has objected, and under Marsy’s Law Yuan will be heard at the hearing, which she plans to attend. A dismissal would not erase the case from law-enforcement records or eliminate his duty to disclose it on state license applications — but Yuan’s biggest concern is that his conviction would no longer appear on a private employer’s background check. Xu did not respond to requests for comment, directly or through his attorney.

Impact on Their Career/Life

For a crime that began as a premeditated-attempted-murder case carrying a potential life sentence, Xu served a single day of credited custody and two years of probation at home with progressively loosened restrictions. Yuan sought nearly $500,000 in restitution; the court ordered $7,058, citing a defense toxicologist’s report concluding cadmium poisoning would not cause long-term health effects — science Yuan disputes. She says she cannot work full time because of lasting impacts, and she published a research paper on the long-term health consequences she and her parents suffered, dedicating it to her father, who died last year: before the poisoning, she wrote, he had only well-controlled hypertension and walked six miles daily; by late last year he was bedbound and unable to eat. Xu’s conviction, the site of his crime and his petition to clear it, now sits at the center of a fight over whether an employer’s background check will ever show what the spy cam recorded.

Sources

San Francisco Standard, “She nearly died from poisoning. Now she’s releasing spy-cam videos of convicted coworker,” Oct. 10, 2026 — source
New York Post, “Berkeley chemical engineer caught on video poisoning coworker,” Oct. 11, 2026 — source
KQED (originally Berkeleyside), “Berkeley Engineer Suspected of Poisoning Colleague Is Charged with Attempted Murder,” Apr. 2, 2019 — source
CBS San Francisco (KPIX 5), “Berkeley Engineer Arrested For Allegedly Attempting To Poison Co-Worker,” Apr. 1, 2019 — source
ABC7 News (KGO), “Berkeley chemical engineer charged with trying to poison co-worker to death,” Apr. 2, 2019 — source
@nypost on X, “Berkeley engineer caught on video poisoning coworker before she suffered horrific health problems,” Oct. 11, 2026 — source