Traces of the deadly nerve agent VX were found on the clothing of the two women accused of murdering Mr Kim Jong Nam.
Mr Kim is the estranged half-brother of North Korean leader Kim Jong Un.
At a court hearing yesterday, government chemist Raja Subramaniam said tests detected a chemical called VX or VX acid on Siti Aisyah's sleeveless shirt and on the T-shirt Vietnamese suspect Doan Thi Huong was wearing.
The testimony of Dr Raja, who is the head of the Chemistry Department's Centre of Chemical Weapons and Analysis, was the first piece of evidence in the murder trial that linked the two suspects to the nerve agent.
He said VX - which the United Nations classifies as a weapon of mass destruction - will degrade when it reacts with water but it will leave detectable by-products.
Traces of the nerve agent were also found on Doan's fingernail, Dr Raja testified.
Doan, 28, was seen on closed-circuit television camera (CCTV) footage wearing the T-shirt - with "LOL" printed on it - at the Kuala Lumpur International Airport on Feb 13.
It was the same day Mr Kim was attacked while waiting for his flight to Macau.
Doan and Siti Aisyah, 25, an Indonesian, allegedly approached Mr Kim at the airport's departure hall and smeared the VX nerve agent on his face.
A lab test found traces of VX nerve agent on Mr Kim's face, eyes, bag and the jacket he was wearing. Witnesses at the murder trial earlier testified that Mr Kim died from acute VX poisoning.
Dr Raja said pure VX, in its physical form, is colourless, odourless and tasteless.
"A small drop of the nerve agent, equal to about 10mg, is enough to cause a fatal disruption to the nervous system... If the decontamination process was carried out within 15 minutes of being in contact with VX, it would not cause a fatality," he added.
A person can fully decontaminate himself of VX by washing and scrubbing with water, he said.
Dr Raja also agreed that the eye's mucous membrane was the best route of entry for the nerve agent as moisture would accelerate the process of contamination.
He said the eye tissue "has no barrier", and has lots of blood vessels compared with the palm of the hand, which has more fatty tissues.
"So, absorption is rapid through the eyes," he said.
Dr Raja is the eighth witness to testify in the murder trial of Mr Kim. The trial will resume at the Shah Alam High Court in Selangor on Monday.