A former Stanford University graduate medical student charged with spiking her lab mates' water with paraformaldehyde pleaded no contest Tuesday, Dec. 8, to four felony counts of poisoning, the Santa Clara County District Attorney's office confirmed.
Xiangyu Ouyang, 26, of Singapore made the plea in Palo Alto's North County Courthouse to all charges, Deputy District Attorney Anne Seery said. Ouyang faces a maximum sentence of one year in county jail.
Ouyang was arrested on Nov. 11, 2014, for the poisonings, which occurred in the Stanford School of Medicine's Lorry Lokey Stem Cell Research Building in September 2014, according to court documents. She was expelled from the University and banned from all Stanford properties after the incidents came to light. She had been a researcher there for three years.
A Singapore National Science Scholar at the Agency for Science, Technology and Research, she appeared to be under duress while at Stanford and was unsure of herself, witnesses in the lab told police. Described as quiet, shy, meticulous and a good student, she once expressed that she was stressed out, according to a police report.
Ouyang added paraformaldehyde to the bottles of lab colleagues and allegedly sabotaged the research of a senior researcher at the lab, according to court documents. Paraformaldehyde has caused stomach irritation and papillomas in rats and mice when ingested, and it can cause skin irritation in humans, but it is not known to be carcinogenic in humans when ingested, according to the World Health Organization (WHO). It may cause nausea, vomiting and diarrhea. Prolonged ingestion may affect the kidneys and cause gene mutations.
A lab mate experienced immediate burning to her throat and mouth after drinking from the water bottle she had left on her desk. She then noticed the water smelled like paraformaldehyde, which is readily available in the lab, according to a police report. The colleague began checking her water bottle thereafter, and she discovered the same smell about four times a week for the next two to three months, she told police. She eventually threw the bottle away but first preserved some of the suspicious substance, which was later found to contain 884 parts per million of paraformaldehyde, according to police.
A second lab colleague also experienced multiple incidents during September or October in which her water bottle appeared to have been tainted with paraformaldehyde, according to the police report. She began to salivate uncontrollably and felt her esophagus contracting, according to the report.
The water bottle of a third colleague was later tested and found to contain paraformaldehyde, according to the police report.
Ouyang was also accused of sabotaging a fourth colleague's research. In mid-August 2014, stem cells the colleague had successfully grown started to mysteriously die overnight. The problem occurred a second time.
The colleague discovered Ouyang standing in front of the incubator with the door open and an open bottle of Trypsin, an enzyme that causes cells to detach and float up, on the incubator hood, the colleague told police.
To determine if she was being deliberately targeted, the colleague mislabeled some of her cell plates in her incubator and left others with her name on them. All of the experiments with her name on them died while the others did not. The colleague then reported the incident to the head of the lab. Video footage later obtained also placed Ouyang in the lab where she was doing no work, according to the police report.
Ouyang admitted to tainting the water bottles and to destroying her lab mate's stem cells. Prior to adding paraformaldehyde to the bottles, she had started putting dish-washing liquid in her own water at home and drinking it. She progressed to spiking her water with random chemicals she found at the lab, she told police.
Ouyang told police she did not have animosity toward her colleagues, and there was not a sense of competition as their projects did not overlap. She had insomnia and dizziness and felt a disconnection from reality starting in September, she told police.
The thought of her colleagues drinking the tainted water was "terrifying," she said, but she never checked on their welfare nor warned them. She was crying out for help, she told police, and she was sorry that things went so far.
Seery, the prosecutor, said there was little negotiating in this case due to its nature.
"We don't know why she did this. The conduct was clearly dangerous, and it was going on for quite some time. Thankfully, all of the students are fine. We always thought that the charging was appropriate and reflective of her conduct. I'm glad we reached a resolution," she said.
Stanford University officials said they immediately took action after learning of the crimes.
"This was a serious matter that the university addressed swiftly and reported to law enforcement. We are glad that the judicial process is concluding, and that everyone involved can move beyond this distressing episode," Lisa Lapin, associate vice president of university communications, said in an email.
Ouyang, whose parents are professors in Singapore, was in the U.S. on a student visa. She could be deported after sentencing or after her jail term, Seery said. She will most likely also be ordered to pay restitution to her victims after the court receives an interim probation report. Sentencing is scheduled for Jan. 15, 2016.
Her attorney could not immediately be reached for comment.