A*STAR scholarship holder Ouyang Xiangyu, 26, who is accused of poisoning the drinking water of two Stanford University students, will appear before a US judge on May 15.
She will appear before the Palo Alto Courthouse, the fifth time she has been in court since her arrest last November.
Ouyang, who has been expelled from Stanford University, is charged with four counts of tainting the water bottles of two of her lab mates between September and November last year.
The graduate student is also accused of sabotaging a lab mate's experiments from mid-August.
Court documents reveal that she had allegedly been struggling with mental health issues, which she said started around September.
Her first court appearance was on Dec 1. Her lawyer at the time, Ms Adrienne Dell, requested a confidential examination by a mental health expert.
On the second court date, Dec 29, the Superior Court judge ordered the appointment of the expert to "prepare a confidential report for defence counsel".
It is expected Ouyang will plead not guilty due to insanity.
Attempts to contact her and her current lawyer, Mr Jeffrey Hayden, were not successful.
When speaking to the police on the date of her arrest, Nov 16, she revealed that she started to suffer from severe insomnia and dizziness in September.
She told the police she was psychologically unstable, depressed, stressed and very dizzy.
A few months before her arrest, she said she had spoken to a counsellor about her condition and was referred to a psychiatrist.
Although the psychiatrist prescribed anti-depressants, Ouyang said they caused her headaches to become worse.
She did not feel like herself and stopped taking the medication.
She admitted to tainting the water in two water bottles other than her own, saying that she used a pipette to put toxic paraformaldehyde (PFA) into the bottles, but could not provide a reason for her actions.
The two lab mates who said they drank the water complained of a burning sensation in their throats and reported the matter to university officials. They were not hospitalised.
When Ouyang was asked why she did what she did, she told the police: "I wasn't very clear about why I was doing it.
"I know it's wrong."
PFA is a preservative used in mortuaries and medical laboratories and can cause severe skin irritation. It can be lethal when ingested.
Ouyang apologised for not taking care of her personal issues and letting things get out of hand.
"I am truly sorry for what had happened, but I really didn't mean to harm people," she told the police.
She is currently out on US$50,000 (S$68,000) bail, and is barred from leaving the United States.
This article was first published on April 10, 2015.
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