The Criminal Court has acquitted Sararat Rangsiwuthaporn, commonly known as "Am Cyanide", who has been dubbed Thailand's worst serial poisoner, of the premeditated murder of a greengrocer.
The defendant was accused of lacing a vegetable salad with cyanide, causing the victim's death in 2022.
The court ruled on Tuesday that prosecutors had failed to prove beyond a reasonable doubt that she poisoned Rosjarin Nilnoi.
According to the prosecution, Sararat committed the murder to avoid repaying a 60,000-baht debt she owed the victim.
The victim's husband brought the case after Sararat was accused in a series of alleged cyanide poisoning deaths in 2023.
The court found that the prosecution's evidence was insufficient in this case to establish that cyanide caused the victim's death or that Sararat administered the poison.
A doctor who treated the victim testified that Rosjarin's blood was highly acidic, which could have resulted from either a severe infection or poisoning, but was unable to confirm that the poison was cyanide, identify the type of toxic substance involved, or determine how it entered the victim's body.
The court also found weaknesses in the testimony of one of the prosecution's key witnesses, an employee of the victim. The witness claimed to have seen Sararat deliver the salad and said she recognised the defendant's vehicle because she frequently visited the victim.
Under cross-examination, however, the witness was unable to identify the make of the vehicle, leading the court to conclude that the testimony was not sufficiently reliable to prove that Sararat delivered the poisoned food.
The court also rejected the prosecution's alleged motive.
Prosecutors argued that Sararat killed the victim to erase a 60,000-baht debt, but the court found that the victim had pawned her car to Sararat for 100,000 baht and had already repaid 50,000 baht.
After the victim's death, Sararat told the victim's husband that he owed 600,000 baht to redeem the vehicle.
Following negotiations, he paid 300,000 baht and recovered the car. The court ruled that these circumstances did not establish a credible motive for murder and that the prosecution had failed to present evidence directly linking Sararat to the alleged poisoning.
Prior to Tuesday's ruling, the Criminal Court had already delivered judgments in four murder cases involving Sararat.
In the first case, the court sentenced her to death for poisoning Siriporn Khanwong, who died near a riverside pier in Ban Pong district, Ratchaburi province.
In the second case, involving the poisoning death of Pol. Capt. Nipah Saengchan, the court initially imposed the death penalty but commuted the sentence to life imprisonment after finding that her testimony had been beneficial to the proceedings.
In the third case, concerning the poisoning death of engineer Nittaya Kaew Buppha in Nakhon Pathom province, the court acquitted her, ruling that there was insufficient evidence to prove that she possessed cyanide or had a financial motive linked to the victim's property.
In the fourth case, involving the poisoning death of Pol. Capt. Sukanya Wimonmart, a former deputy finance inspector at Phu Pha Man Police Station in Khon Kaen province, the court found that she had laced the victim's drink with poison, causing her death.
Although the court initially sentenced her to death, the penalty was reduced by one-third, leaving her with another life sentence.
