Singaporean A*Star scholarship holder Ouyang Xiangyu, 26, pleaded not guilty at the Santa Clara County Superior Court on Friday to four counts of poisoning her laboratory mates.
The former Stanford University graduate student's appearance at the Palo Alto Courthouse in California was her fifth since her arrest last Nov 16 for poisoning the drinking water of two lab mates between September and November last year.
Prior to those incidents, she had also allegedly sabotaged another lab mate's experiment from mid-August last year.
Ouyang, who has been described by fellow students as quiet and shy, became a full member of the Nusse Laboratory at the department of developmental biology at Stanford in June last year. Last month, the university said she had been expelled.
According to court documents, she had been experiencing severe insomnia and dizziness since September last year, and admitted to police that she had indeed put paraformaldehyde in two water bottles belonging to her lab mates.
The substance is a preservative used in mortuaries and medical laboratories, and can cause severe skin irritation. It can be lethal when ingested.
Acquaintances who spoke to The Sunday Times said she had often seemed stressed by work.
But not all who have worked at the Nusse Lab share Ouyang's negative experience.
Junior principal investigator in the Institute of Medical Biology at the Agency for Science, Technology and Research (A*Star) Lim Xinhong, 32, said he had a "very positive experience" but had left the Nusse Lab before Ouyang joined.
"I really enjoyed interacting with my lab mates, learning from their constructive critiques and hanging out with them outside of lab," said Dr Lim.
"The Stanford Developmental Biology department was very collegial, and there was a general strong atmosphere of collaboration and community," he added.
Ouyang is currently out on bail and will return to court on Aug 3, for a readiness hearing - which will assess if the case is ready for trial, according to a spokesman for the court.
The preliminary hearing, where items of evidence and the facts of the case will be presented, is scheduled for Sept 4.
Ouyang declined to speak to The Sunday Times when the paper tried to reach her for comment last Friday. Attempts to contact her lawyer have also been unsuccessful.
This article was first published on May 17, 2015.
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