Former Stanford grad student accused of poisoning classmates

A Stanford University student walks in front of Hoover Tower on the Stanford University campus in Palo Alto, California. A Stanford University student walks in front of Hoover Tower on the Stanford University campus in Palo Alto, California. Photo: Associated Press Photo: Associated Press Image 1 of / 4 Caption Close Former Stanford grad student accused of poisoning classmates 1 / 4 Back to Gallery

A former graduate student at Stanford University is facing four felony charges of attempting to poison her classmates by secretly dumping a chemical into their water bottles, according to court documents.

Starting in September, medical students working in a lab at the university began to notice an odd smell — later determined to be paraformaldehyde — coming from water bottles that had been left out, documents showed.

On a few occasions, some students complained of irritation and burning after drinking from their water bottles, according to a criminal complaint filed with the Santa Clara County district attorney’s office first reported by the Fountain Hopper, an anonymous campus publication.

“I think someone is trying to kill me!” exclaimed one of the victims after sipping from an allegedly tainted water bottle, according to a statement given to the Stanford University Department of Public Safety.

Exposure to paraformaldehyde can cause skin irritation, inflammation, respiratory illness and — in severe cases of overexposure — death. The chemical is used in pesticides and disinfectants.

The suspect, 26-year-old Xiangyu Ouyang of Singapore, was reportedly reclusive — her labmates described her as “awkward” and “strange” — but none of the victims told police she had shown animosity toward anyone.

In November, when investigators began questioning victims, Ouyang checked herself into a hospital for mental health issues and was placed on a psychiatric hold, according to Santa Clara County Superior Court documents.

After she was released, Ouyang admitted to tampering with at least two water bottles, and told police she had put paraformaldehyde in her own water bottle but had suffered no adverse effects.

Ouyang told police she had been suffering from severe insomnia and dizziness caused by anti-depressants and had stopped taking her medication before the alleged poisoning began, according to court papers.

“I am truly sorry for what happened, but I really didn’t mean to harm people,” she was quoted as saying. “It was me crying out for help.”

Lisa Lapin, a spokeswoman for the university, said Ouyang is no longer a student at the university.

“This was a sad, heartbreaking situation for everyone involved,” Lapin wrote in an e-mail. “This was a confined, isolated circumstance and there was no threat to the broader campus community. The university has been providing support to the group impacted.”

Ouyang was arrested Nov. 16 and has been charged with four counts of poisoning — all felonies — according to the district attorney’s office.

Court documents indicate Ouyang is undergoing a psychiatric evaluation and may pursue an insanity defense. She is due to next appear in court May 15.

Kale Williams is a San Francisco Chronicle staff writer. E-mail: kwilliams@sfchronicle.com Twitter: @sfkale