The half-brother of North Korea's leader was carrying bottles of the antidote to the toxin used when he was killed earlier this year, reports say.
Kim Jong-nam died in February at Kuala Lumpur airport after highly toxic VX nerve agent was rubbed on his face.
The 12 bottles contained Atropine, which is used to combat the effects of nerve agents including VX, local media said a toxicology report showed.
They were found in a backpack Mr Kim was carrying when he was killed.
A doctor told the Malaysian High Court the antidotes were handed to her for testing by police, The Star newspaper reports.
"I received the items together with seven other exhibits from police who handed it to me... on March 10 for toxicology tests," she said.
Two women, from Indonesia and Vietnam, have pleaded not guilty to the killing.
Doan Thi Huong, 29, and Siti Aisyah, 25, are accused of wiping the toxin in Mr Kim's face on 13 February.
They say they were tricked and thought they were taking part in a TV prank. They face death by hanging if convicted.
CCTV footage from the departure lounge of the airport shows two women approach Mr Kim before placing something over his face.
Pyongyang has denied any involvement in the killing, but, in court, prosecutors said four North Korean men were involved.
Kim Jong-nam was largely estranged from his family, after being bypassed for inheriting the leadership in favour of his younger half-brother. He spent most of his time overseas in Macau, mainland China and Singapore.
He had spoken out in the past against his family's dynastic control of North Korea and in a 2012 book was quoted as saying he believed his half-brother lacked leadership qualities.
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