A California engineer who says a colleague's cadmium poisoning left her with lasting health problems has released office surveillance footage after the colleague's felony conviction was dismissed by a court, raising concerns about whether future employers will see his criminal record.

Rong Yuan, 50, says she has been unable to work full time since the poisoning and fears that the dismissal of David Xu's conviction will make it harder for future employers to discover his criminal history through background checks.

Xu, 41, asked an Alameda County Superior Court judge on Monday, 12 October, to dismiss his felony conviction after completing two years of probation in March. The judge granted the petition despite objections from the district attorney's office.

Footage and Lab Results in Cadmium Poisoning Case

Yuan and Xu both worked as metallurgists at Berkeley Engineering and Research, a consulting firm in Berkeley. From October 2017, Yuan noticed a strange taste or smell in food and water left unattended in her office, court documents say. She reported health problems that at times required hospital treatment.

She later installed a camera in her office. Court filings say it showed Xu adding a substance to her water bottle on 11 February and 4 March 2019. Samples from the bottle tested positive for a toxic amount of cadmium, a metal that can cause cancer.

Blood tests found elevated cadmium levels in Yuan and both of her parents, who also became ill after exposure to water from her workplace bottle, according to reports.

Berkeley police arrested Xu at his home in Lafayette on 28 March 2019. He was charged with premeditated attempted murder, with a special allegation of great bodily injury, and two counts of felony poisoning. Bail was set at $2 million (£1.51 million). He pleaded not guilty.

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Plea Deal and Dispute Over Lasting Cadmium Effects

In September 2023, Xu pleaded no contest to one count of poisoning under a deal offered by prosecutors. The attempted murder charge and the other poisoning count were dropped. A no-contest plea carries the same weight as a conviction but is not an admission of the underlying facts.

At sentencing in March 2024, Judge Kimberly Colwell called the agreed one year of probation 'extremely generous, considering everything in this case' and doubled it to two years. 'Please do not touch any poison at all,' she told him. 'Ever. Ever.' Xu spent less than two weeks in custody in total, according to reports.

State engineering regulators objected to the deal. In a memo, they said Xu had expressed concern about Yuan competing with him for work. Police have never publicly confirmed a motive, and Xu has not spoken in detail about the case.

Yuan says the poisoning caused long-term complications. A judge ordered Xu to pay Yuan $7,058 (£5,328.79) in restitution after considering a report submitted by his lawyer from a toxicologist who concluded that cadmium poisoning would not cause long-term health effects. Yuan disputed the report's conclusions, according to the San Francisco Standard.

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