A woman accused of killing a mother and daughter living next door in Busan last year had allegedly poisoned the neighbor’s 15-year-old son before the murder, according to the boy’s testimony at court.

During the first hearing of the double murder case held at Busan District Court on Monday, the sole survivor of the family took the witness stand to recount the Sept. 12 visit by the neighbor, who brought with her a bottle of light purple liquid which she said was a tea made with balloon flower roots, a common food ingredient in Korea known as doraji.

After drinking it, he slept for 15 hours straight, he told the court. When he woke up with a headache the next day, he found his mother and younger sister dead. The woman next door is reported to have visited the family before. On the day of that fateful visit, she is said to have brought along her granddaughter, he added.

The accused neighbor is charged with the murder of the two victims, as well as with the violation of the Narcotics Control Act. The prosecution alleges that the suspect mixed her psychiatric medicine with the doraji tea, fed it to her neighbors and killed two family members.

A postmortem autopsy found sleep-inducing substances in the bodies of the victims were concluded to have died of suffocation. The suspect had been receiving psychiatric treatment since July 2015.

Prosecutors said the suspect, who had no steady job and had financial difficulties paying monthly rent, living expenses and medical bills, killed the victims to steal their valuables.

The accused claims she is innocent.

In her defense, her lawyer argued during Monday's hearing that she had not offered the doraji tea nor had she killed the deceased.