KUALA LUMPUR (Reuters) - Lawyers for two women accused of murdering the estranged half-brother of North Korean leader Kim Jong Un said on Tuesday low enzyme levels in his blood may have been caused by liver disease or hormone pills rather than a lethal nerve agent.

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Indonesian Siti Aisyah, 25, and Doan Thi Huong, 28, a Vietnamese, are charged with murdering Kim Jong Nam by smearing his face with VX, a chemical poison banned by the United Nations, at Kuala Lumpur airport on Feb. 13.

The women have pleaded not guilty, saying they thought they were involved in some sort of prank for a reality TV show. They face the death penalty if convicted.

Nor’ashikin Othman, a chemical pathologist with Kuala Lumpur Hospital, told the court outside Kuala Lumpur blood samples taken from the victim showed low levels of cholinesterase - an enzyme needed in muscle control - which “could be caused by exposure to poison such as insecticide or a nerve agent” such as VX or Sarin.

But she agreed with the defense that low enzyme levels could also have been due to other causes such as liver disease or the taking of female hormones by a man.

“Yes, the enzyme levels could be slightly lower by the taking of hormone pills by a man,” she said.

In response to a question, Nor’ashikin also said it was possible the accused had had no contact with VX whatsoever as their blood samples yielded normal levels of cholinesterase.

But they could have also been exposed to a low dose of the poison, washed their hands with soap and water or ingested an antidote, she said.

Siti and Huong are accused of smearing the deadly nerve agent on the victim’s face and eyes. The trial has so far referred to the victim as Kim Chol, the name on the passport used by Kim Jong Nam.

The post mortem report, made available to the media, said that VX was detected on swabs of Kim Jong Nam’s eyes and face, in the blood, plasma and urine.

The report described the victim’s body as covered with tattoos. These include a large black tattoo on the chest of a man with two fish-like fingers, and one of “abstract-like motifs” on his upper right arm that extends to his upper back.

Police have also named four North Koreans as suspects in the case and an Interpol red notice, an international alert just short of an arrest warrant, has been issued for the four, who remain at large.

The trial continues on Wednesday.