SHAH ALAM, Malaysia (AP) — A pathologist says the estranged half brother of North Korea’s leader had extremely low levels of an enzyme vital for nervous system function due to poisoning after being attacked at a Malaysian airport in February.

Chemical pathologist Nur Ashikin Othman testified Tuesday at the trial of the two women accused of smearing VX nerve agent on Kim Jong Nam’s face.

Nur Ashikin said the two suspects had normal enzyme levels in their blood tests. She said the potency of VX depends on the dosage or concentration, the type and duration of exposure and whether decontamination measures were made. The defense has asserted the two women were not exposed to VX.

Siti Aisyah of Indonesia and Doan Thi Huong of Vietnam pleaded not guilty to murder as their trial opened Monday.