However, experts say that his plan to use an antidote was also fatally flawed.

“The presence of atropine on his person would confirm the fear of chemical fratricide,” said Cindy Vestergaard, an expert on chemical weapons at the Stimson Center in Washington, but Kim appeared to have been “poorly advised on antidote efficacy.”

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Details of the antidote were revealed this week at the Malaysian High Court, where two women — Indonesia’s Siti Aisyah, 25, and Vietnam’s Doan Thi Huong, 29 — stand accused of smearing the VX agent over Kim's face as he entered an airport terminal in Kuala Lumpur on Feb. 13.

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Lawyers for the two women say they were duped into carrying out the attack, which is widely believed to have been instigated by North Korean agents in a bid to remove a potential rival to Kim Jong Un.

The elder Kim became incapacitated after a substance was smeared on his face and died shortly afterward. Doctors later ruled that the cause of death was “acute VX nerve agent poisoning,” referring to the banned substance also known as N-2-Diisopropylamino Ethyl methylphosphonothioate.

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According to local media, a government toxicologist serving as a witness for the prosecution told the court Wednesday that Kim had been carrying 12 bottles of atropine antidote in his bag when he was killed. Atropine can provide “primary protection against exposure to chemical nerve agents and insecticide poisoning,” according to the American Society of Health-System Pharmacists.

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It is unclear in what form the drug was being carried or whether Kim had tried to administer it after he was attacked. Experts say that it is unlikely the drug would have done much good for him, even if it was administered immediately.

“Atropine by itself is not an effective antidote for VX poisoning,” said Matthew Meselson, a professor of biochemistry at Harvard University and a board member of the Center for Arms Control and Non-Proliferation. Meselson said auto-injectors supplied by the U.S. Army to combat nerve agent poisoning contain not only atropine but also pralidoxime, another agent that helps prevent VX's toxic effects.

Vestergaard noted that some reports said the antidote was being carried in a tablet form, but that it can take at least 15 to 20 minutes for atropine to reach the bloodstream if orally administered. “By then, VX will already be wreaking havoc on the body’s nervous system (including vomiting, making orally-administered antidotes even more useless),” she wrote in an email, adding that an oral form of atropine could only provide “a false sense of security.”

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The presence of atropine in Kim's bag would appear to suggest that he knew he was at risk. Though he was generally kept out of the public eye by the North Korean government, he was often viewed as a potential rival to Kim Jong Un because of his openness to reforms and direct bloodline to North Korea's founder, Kim Il Sung. Intelligence officials in Seoul said that Kim Jong Un had put a “standing order” out for his older half brother's assassination several years ago.

There were also reports in a South Korean newspaper that he had tried to defect — a move that would have been extremely embarrassing for Pyongyang.

Sue Mi Terry, a former North Korea analyst at the CIA now at the Center for Strategic and International Studies, said that it is not surprising that Kim Jong Nam thought he was a target — especially after his uncle and close ally, Jang Song Thaek, was killed in 2013.

“What is surprising is that Kim Jong Nam might have known the likely method of the attack,” Terry said. “If that is the case, it's likely that a foreign intelligence service might have given him a warning.”