The women, in their 20s, have denied murdering Kim Jong Un's estranged half-brother by smearing VX nerve agent on his face as he waited for a flight to Macau. They face death by hanging if found guilty.

Pressed by Aisyah's lawyer Gooi Soon Seng, chemical weapons expert Raja Subramaniam told the Shah Alam high court the Malaysian lab where the nerve agent VX was tested is not among centres designated by the Organisation for the Prohibition of Chemical Weapons (OPCW).

Labs need to maintain a certain standard to be on the OPCW list, and must participate in proficiency testing at least once a year. The Malaysian lab had not undergone this, a process which Raja said was "voluntary".

Samples of the nerve agent, considered a weapon of mass destruction, had also not been sent to the OPCW depite the body having made a request, said Gooi.

Prosecutors on Thursday closed their case after 39 days of hearings that saw 34 witnesses testify. A verdict is not expected for some months.

Prosecutor Wan Shaharuddin Wan Ladin told AFP their case was "watertight", and he expects the two young Southeast Asian women to take the witness stand to defend themselves.

But Gooi rubbished the prosecution's confidence: "Where is the direct evidence that Siti applied anything (on Kim Jong Nam)? We are confident she will be acquitted." (AFP)