Engineer Who Poisoned Coworker for 18 Months Seeks Felony Dismissal After Serving Just One Day in Jail

A California engineer who secretly poisoned his female coworker with toxic heavy metal cadmium over an 18-month period is seeking to have his felony conviction formally dismissed after serving just one day in jail

Shocking surveillance footage released on Saturday, 10 October 2026, captured David Xu, a former principal metallurgist at Berkeley Engineering and Research, surreptitiously tampering with colleague Rong Yuan's desk water bottle.

For nearly two years between 2017 and 2019, Yuan endured excruciating gastrointestinal agony, relentless vomiting, severe hair loss, and repeated emergency hospital admissions that left her fearing terminal stomach cancer.

Laboratory analyses subsequently revealed that her office drinking water had been contaminated with cadmium levels reaching 3.5 million times the federal safety threshold, also poisoning her elderly parents.

Despite originally facing attempted murder charges carrying potential life imprisonment, Xu secured a lenient plea agreement under former Alameda County District Attorney Pamela Price, receiving two years of probation and a £5,200 ($7,058) restitution order.

Having completed his probation in March 2026, Xu's petition to expunge his criminal record at Alameda County Superior Court on 12 October has triggered profound outrage from his surviving victim.

Hidden Camera Catches Engineer Tampering With Coworker's Water Bottle

For nearly two years, Yuan struggled with unexplained symptoms, including persistent vomiting, hair loss and repeated hospital visits.

Despite undergoing medical examinations and seeking treatment, she could not determine what was making her ill.

According to an investigation by The San Francisco Standard, Yuan began suspecting someone was tampering with her drinking water after her mother noticed an unusual sour taste in a bottle she had brought home from work.

In February 2019, Yuan installed a hidden camera near her office desk. Surveillance footage shared with ABC7 News shows Xu approaching Yuan's workstation and tampering with her drinking water.

The first recording, dated 11 February, captured Xu approaching her workstation and reaching toward where her water bottle was kept.

A second recording, taken on 4 March, showed him pouring a substance from a small white container into the bottle. He returned approximately 30 seconds later, rotated the bottle and walked away.

'My blood was frozen,' Yuan recalled upon seeing the footage. 'I almost died. I experienced death so, so close so many times. I cannot let him go.'

Yuan subsequently handed the recordings to police, triggering an investigation that led to Xu's arrest later that month.

Coworker Poisoned With Cadmium as Health Deteriorated

Investigators discovered that Yuan's food and drinking water had been contaminated with cadmium, a toxic heavy metal that can cause serious health problems.

Laboratory findings show that samples from her water bottle contained cadmium concentrations up to 3.5 million times the federal drinking water limit.

Yuan began experiencing symptoms in 2017, shortly after joining Berkeley Engineering and Research, where both employees worked as metallurgists.

Over the following months, Yuan experienced severe vomiting, dry heaving and other symptoms that repeatedly sent her to hospital. At one point, she feared she might have stomach cancer.

Her parents were also exposed to cadmium after consuming water from the contaminated bottle. Police testing detected the substance in blood samples taken from Yuan and both parents.

Despite her worsening condition, Xu reportedly maintained a seemingly sympathetic attitude towards his colleague.

In November 2018, after Yuan informed coworkers that she was too ill to come to work, Xu suggested she work from home and raised the possibility of mould in the office.

Why Did David Xu Receive Just One Day in Jail?

Xu was arrested in March 2019 and initially faced charges including premeditated attempted murder and two felony counts of poisoning. He could have faced life imprisonment if convicted of the most serious charge.

However, the case took a different direction in September 2023, when Xu accepted a plea agreement offered under then-Alameda County District Attorney Pamela Price.

Under the agreement, Xu pleaded no contest to a single felony count of poisoning, while the attempted murder charge was dropped.

The deal included one year of probation and credit for one day already spent in custody, rather than an additional custodial sentence.

At his March 2024 sentencing hearing, Judge Kimberly Colwell described the agreement as 'extremely generous, considering everything in this case,' according to the reported court transcript.

The judge increased Xu's probation period to two years and ordered him to stay away from Yuan and her parents. Yuan had sought nearly $500,000 in restitution, but the court ordered Xu to pay $7,058.

Why Is Xu Seeking To Have His Felony Conviction Dismissed?

After completing his probation in March 2026, Xu filed a petition to have his felony conviction dismissed under California law, a process commonly called expungement.

The court scheduled a hearing on his request at Alameda County Superior Court on Monday, 12 October.

California law generally allows eligible defendants who successfully complete probation to have their convictions dismissed, provided they satisfy the relevant legal requirements. However, such a dismissal does not completely erase a criminal record.

Law enforcement authorities may still access case information, and the conviction may remain relevant to future criminal proceedings or professional licensing applications. According to court records cited in the investigation, the district attorney's office is opposing Xu's petition.

Victim Questions Justice System as Felony Dismissal Looms

For Yuan, the possibility of having Xu's felony conviction dismissed has raised further concerns about whether the legal system adequately addressed what happened to her.

She has reported continuing health problems that affect her ability to work full-time. Yuan is also concerned that dismissal could make it harder for prospective employers to discover Xu's conviction through routine background checks.

'This legal system already failed me,' she said. 'This is my last resort.' The case has also drawn criticism online, with some social media users questioning why Xu received probation rather than a lengthy prison sentence.

Investigators have never established a definitive motive explaining why Xu targeted his colleague over an extended timeframe.

Yuan continues to seek legal remedies, arguing that workplace perpetrators of toxic chemical assaults should not be granted clean criminal records while victims suffer permanent physical injuries.