The substance that ended the life of Mr Kim Jong Nam, the half- brother of North Korean leader Kim Jong Un, remains as much a mystery as the motivations behind the killing.
A police officer was quoted as saying that the poison used at a Kuala Lumpur International Airport on Monday morning, believed to be a liquid, was "more potent than cyanide".
But Ms Lim Chin Chin, senior consultant forensic scientist with The Forensic Experts Group in Singapore, said it is too early to speculate what substance it was without further clues - such as its appearance or smell, how the victim was exposed and the victim's symptoms.
"There are many substances that can kill if used in the wrong amounts," she said.
Some well-known and potent poisons include arsenic, which has been used for centuries by people on their enemies, and sodium cyanide, which is used in illegal cyanide fishing.
Sodium cyanide is an example of an "easy" poison because it is soluble in water and only a small amount is needed, said Ms Lim.
There is also sarin, which killed or injured scores of people in the Tokyo subway in a domestic terror attack in 1995.
These poisons can be inhaled, ingested or absorbed through the skin.
"A lot of these chemicals are controlled items in Singapore... But in other cities in Asia, some of them are quite easily available," said Ms Lim.
Under Singapore's Poisons Act, more than 1,000 substances are listed as poisons, while more are listed as hazardous substances under the country's Environmental Protection and Management Act.
Others, such as sarin, are listed as chemical weapons under the international Chemical Weapons Convention, which Singapore ratified in 1997.
Past poisonings suspected to have been politically motivated include that of former Russian Federal Security Service agent Alexander Litvinenko, who died after drinking tea laced with radioactive polonium-210 in 2006.
And back in 1896, Sultan Sheikh Hamad bin Thuwaini of Zanzibar died from suspected poisoning by his cousin Khalid bin Barghash, who proclaimed himself sultan, setting off a war with the British.
This article was first published on Feb 16, 2017.
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