After the lab visit, defense lawyers are expected to cross-examine Raja, who testified last week that VX was found on the women's clothing as well as on Kim Jong-nam's face, eyes, clothing, and in his blood and urine samples.

This week, prosecutors say they will present airport security videos that show the two women carrying out the attack and indicate they knew they were handling poison.

Defense lawyers have said the women were duped by suspected North Korean agents into believing they were playing a harmless prank for a hidden TV-camera show.

Doan Thi Huong of Vietnam and Siti Aisyah of Indonesia pleaded not guilty at the start of their trial last week to charges of murder that carry a mandatory death sentence if they are convicted.

Kim, the eldest son in the current generation of North Korea's dynastic rulers, was believed to be a family outcast who may have been perceived as a threat by the nation's leader, his youngest sibling Kim Jong-un.

VX is banned by an international treaty as a weapon of mass destruction but is believed to be part of North Korea's chemical weapons arsenal. (AP)