Traces of the VX nerve agent were found on the clothing of the two women on trial for the murder of Kim Jong-nam, North Korean leader Kim Jong-un’s estranged half-brother, a chemical expert told a Malaysian court on Thursday.

Raja Subramaniam, head of the Malaysian government’s Centre of Chemical Weapons and Analysis, said they found residues of VX, a colourless and odourless nerve agent deemed by the UN as a weapon of mass destruction, on the clothes of the two accused, Siti Aisyah of Indonesia and Doan Thi Houng of Vietnam, reports Efe news.

He also testified that based on research, the same amount of VX would be 26 times less potent on the palms of human beings as compared to their cheeks.

The two women were accused of smearing the poison with their bare hands on Kim Jong-nam’s face on February 13, when he was about to leave for Macau, where he lived in exile, from the departure terminal of the Kuala Lumpur airport.

Malaysian forensic scientists had found traces of the poison in Kim Jong-nam’s eyes, urine, blood and personal objects.

The prosecution also asked Subramaniam, the only Malaysian to hold a PHD in chemical weapons analysis, about how easy it would be to decontaminate from VX, a substance which he said could kill with even one drop in its purest state, reports Channel News Asia.

“We have to wash with running water plus physical scrubbing for a certain period of time before you get medical assistance,” he said.

Both Doan and Aisyah, who pleaded not guilty when the trial began on Monday, told the police they believed they were playing a prank for a television show and thought the poison was baby oil.

Four North Korean men, who the Malaysian police suspect of plotting the attack, left the country on the same day as Kim Jong-nam’s murder and have been missing since.

South Korea and the US have accused North Korea of masterminding Kim’s murder.

Kim Jong-nam, born in 1971, was the son of late North Korean dictator Kim Jong-il and actor Song Hye-rim and was considered a favourite to replace his father until he fell out of favour in 2001.

The poison from the VX nerve agent kills by sending the nerve system into overdrive causing convulsions, paralysis and eventually death due to respiratory failure.

It was banned under the 1993 chemical weapons convention.