Thailand’s suspected cyanide serial killer “Am Cyanide” cleared in a second murder trial after judges ruled prosecutors failed to prove poisoning. Yet Sararat still has two death sentences, two life terms and remains the focus of a murder spree using cyanide.
A woman police believe may be Thailand’s most prolific serial killer has beaten a second murder charge after the Criminal Court ruled prosecutors failed to prove she poisoned a vegetable vendor with cyanide. The acquittal comes despite Sararat “Aem Cyanide” Rangsiwutthaporn already receiving two death sentences and two life sentences in separate cyanide murder cases, while police continue to link her to 14 suspected poisoning deaths in what became one of Thailand’s biggest criminal investigations and one that will never be forgotten.
A woman police believe may be Thailand’s most prolific serial killer has been acquitted of a second murder charge, despite already receiving two death sentences and two life sentences for separate cyanide poisoning murders.
Sararat “Aem Cyanide” Rangsiwutthaporn walked free from the latest prosecution after the Criminal Court ruled prosecutors failed to prove she murdered vegetable vendor Rosjarin “Phi Noi” Nilnoi with cyanide.
Nevertheless, the 39-year-old remains at the centre of Thailand’s biggest suspected serial poisoning investigation. Police still suspect she administered potassium cyanide to 14 people between 2015 and 2023.
Court clears Am Cyanide in fifth murder trial but police still suspect her over 14 poisoning deaths
Tuesday’s verdict came in Sararat’s fifth murder trial. Prosecutors accused her of premeditated murder after alleging she mixed potassium cyanide into a vegetable salad.
They said Rosjarin later ate the meal, suffered a seizure and died in hospital. Prosecutors further argued the killing was driven by a financial dispute over a debt of ฿60,000. Sararat pleaded not guilty throughout the proceedings.
The judgment was delivered at 10 am in Courtroom 813 of the Criminal Court. Judges ruled the prosecution had failed to establish a direct link between Sararat and the alleged poisoning. More importantly, they found the medical evidence did not prove cyanide caused the victim’s death. As a result, the court dismissed the charge.
The court traced the case back to March 2023, when investigators began uncovering a string of suspected cyanide poisonings. At that point, Rosjarin’s husband began questioning his wife’s sudden death in 2022. He believed it could be linked to the growing investigation. In response, he filed a criminal complaint accusing Sararat of deliberately poisoning his wife with contaminated food.
Medical evidence and key witness testimony fail to convince court of cyanide poisoning
During the trial, prosecutors relied heavily on medical testimony. The physician who treated Rosjarin told the court her blood showed severe metabolic acidosis. The condition meant her blood had become dangerously acidic. However, the doctor explained it could result from either severe infection or poisoning.
Crucially, the witness could not identify cyanide as the poison. Nor could the doctor identify any other toxic substance. The physician also could not explain how poison entered the victim’s body. Likewise, the witness could not determine whether another person administered it. Judges said those unanswered questions left major gaps in the prosecution’s case.
Separately, prosecutors called one of Rosjarin’s employees. The witness claimed to have seen Sararat deliver the vegetable salad. The employee said the defendant’s vehicle was familiar because she visited the victim regularly.
Under cross-examination, however, the witness could not identify the vehicle’s make or model. That inconsistency immediately damaged the evidence. Consequently, the court ruled the testimony was unreliable.
Financial motive over ฿60,000 debt rejected as judges dismiss the prosecution’s case on many fronts
The alleged financial motive also collapsed under scrutiny. Prosecutors claimed Sararat wanted to eliminate a creditor over a ฿60,000 debt. Court records, however, revealed a different financial arrangement. Rosjarin had pawned her car to Sararat for ฿100,000. She had already repaid half that amount before her death.
After Rosjarin died, Sararat demanded that her husband pay ฿600,000 to recover the vehicle. Eventually, both sides negotiated the amount down to ฿300,000. The husband paid the reduced figure and recovered the car. Notably, judges ruled those events did not establish a convincing motive for murder. Instead, they weakened the prosecution’s argument.
Taken together, the medical evidence, witness testimony and financial records failed to prove the charge. Accordingly, the Criminal Court acquitted Sararat of murdering Rosjarin.
The verdict marks Sararat’s second acquittal among the first five murder cases completed against her. Even so, she remains convicted in three other killings.
Three convictions and two acquittals leave Am Cyanide facing life terms and death sentences
The first trial ended with a death sentence for the murder of Siriporn “Koi” Khanwong. Siriporn died near a riverside pier in Ban Pong district of Ratchaburi province. The court found Sararat guilty of poisoning her with cyanide.
The second case centred on the death of Pol Maj Nipa Sangchan, known as “Inspector Pu”. Again, judges imposed the death penalty. Later, the sentence was commuted to life imprisonment because Sararat’s testimony benefited the proceedings.
On another front, the third murder trial ended differently. It concerned engineer Nittaya Kaewbuppha in Nakhon Pathom province. Judges acquitted Sararat after finding insufficient evidence that she possessed cyanide. They also found no proven financial motive.
The fourth prosecution involved Pol Capt Sukanda “Captain Nui” Wimonmal, a former finance officer at Phu Pha Man police station in Khon Kaen province. Judges convicted Sararat of poisoning her. They imposed another death sentence. Later, that sentence was reduced by one-third, resulting in life imprisonment.
Police still link Am Cyanide to 14 suspected murders despite latest acquittal by the Criminal Court
The latest ruling means five murder trials have now concluded. Three produced convictions. Two ended in acquittals. Meanwhile, numerous other investigations remain linked to the wider cyanide inquiry.
Investigators believe Sararat poisoned victims to avoid debts or steal money and valuables. Police also linked her to heavy online gambling. In parallel, detectives examined large bank transfers during the investigation. They further alleged attempts were made to conceal evidence after several deaths.
Sararat, a native of Kanchanaburi province, became known nationwide as “Aem Cyanide” after investigators reported finding cyanide in victims’ bodies. Police arrested her on April 25, 2023. She was pregnant when officers took her into custody.
Bangkok Court sentences serial killer Am Cyanide to death as 14 more murder cases head for Prosecution
Biggest criminal case in Thai history to be finalised, on Friday against suspected serial killer Am Cyanide
As part of the investigation, police completed their criminal inquiries in June 2023. Around the same period, Sararat miscarried during the fifth or sixth month of her pregnancy.
Tuesday’s ruling does not affect the convictions already secured in the earlier murder trials. Instead, it reflects the court’s findings in the death of Rosjarin alone. Ultimately, judges ruled prosecutors failed to prove cyanide caused the victim’s death.
They also rejected key witness testimony and the alleged financial motive. For those reasons, Sararat “Aem Cyanide” Rangsiwutthaporn was acquitted, while her previous death sentences and life sentences remain in force.
Join the Thai News forum, follow Thai Examiner on Facebook here
Receive all our stories as they come out on Telegram here
Follow Thai Examiner here
Further reading:
Am Cyanide sues activist who raised alarm over alleged killing spree. Former lawyer summoned
Am Cyanide touched by the evil of online gambling sites where she lost as much as ฿1 million a day
Police to arrest serial killer suspect’s husband, 10 more charges for gambling addict ‘Am Cyanide’
Thailand’s biggest serial killer suspect legally protected from the death penalty as horror grows
Damning evidence mounts against what police now believe to be a prolific cyanide serial killer
Killer sentenced to death for the 2nd time for the murder of a woman 7 months after being paroled
Sadistic rapist, drug dealer and serial murderer is sentenced to life in prison by Thon Buri court
Death sentence for murderous trio who executed a loving Thai wife and her UK husband in Phrae
93% of Thai people want to see the death penalty put to use to curb shocking murders and drug gangs
