In a case with a thousand plot twists, there has been but one constant in the murder investigation of Kim Jong Nam: Nothing is ever what it seems.
The victim himself - the playboy half brother of North Korean leader Kim Jong Un - was traveling under false papers when he died and had to be identified using DNA. The two women accused of killing him turned out to be hired dupes, paid a few dollars to perform what they thought was a reality-TV stunt.
Stranger still was the murder weapon, liquid VX, a toxin so powerful that a few drops rubbed onto the skin killed the victim in minutes, yet it failed to harm the two women who applied the poison with their bare hands. Even more mysterious: Why North Korea would go to extravagant lengths to use a battlefield-grade chemical weapon on foreign soil, only to work equally hard to cover its tracks.
For the prosecutors preparing for the first court hearings later this month, some of the mysteries behind Kim Jong Nam's death inside a Malaysian airport terminal will likely never be resolved. But nearly five months after the killing, U.S. and Asian officials have a clearer view of the attack's significance. In carrying out history's first state-sponsored VX assassination in a country 3,000 miles from its borders, North Korea has demonstrated a new willingness to use its formidable arsenal of deadly toxins and poisons to kill or intimidate enemies on foreign soil, analysts say.
Seen in the light of North Korea's recent flurry of provocative missiles tests, Kim Jong Nam's killing now looks to many experts like a proving exercise for a weapons system - in this case, a robust chemical-weapons stockpile that Pyongyang is thought to have built over decades and kept carefully under wraps.
"The choice of weapons was not accidental," said Sue Mi Terry, a former senior analyst on North Korea at the CIA and currently managing director for Korea at the Bower Group Asia. "Everything about this incident was intended to send a message."
U.S. and South Korean intelligence agencies have long believed that North Korea possesses significant stores of the nerve agents VX and sarin - and probably biological weapons as well - but in the past, such arsenals were assumed to be intended as a deterrent against foreign attacks. But in the attack on Kim Jong Nam, North Korea revealed a strategy for using chemicals that looks a lot like cyberwarfare: limited, highly secretive attacks that can damage an enemy without inviting massive retaliation.
Whether Kim Jong Un would risk such an attack against a foreign government - even the United States - is unclear. But the February incident is a reminder that North Korea has options for striking targets abroad that do not hinge on the country's ability to build an intercontinental ballistic missile capable of reaching the U.S. mainland, current and former U.S. officials say.
"North Korea is bad enough when you're talking about their nuclear and missiles program," Rebecca Hersman, a former Defense Department deputy assistant secretary for countering weapons of mass destruction, said at a recent policy forum. "But I think we ignore their chemical and biological programs truly at our own peril."
Kim Jong Nam probably knew an attack was coming, though he might not have imagined where, or how.
The 45-year-old eldest son of dead North Korean leader Kim Jong Il had been living in exile in the Chinese province of Macau since 2003, and he had been a probable candidate for assassination since his younger half brother took control of the country in late 2011, claiming the job that had once been promised to him. A vocal critic of North Korea's repressive communist government, his fate was likely sealed in 2013 when the newly installed leader ordered the execution of Jang Song Thaek, a prominent North Korean defense official and Kim Jong Nam's uncle and longtime protector.
But when he strode into Kuala Lumpur's KLIA2 airport with his light jacket and backpack on Feb. 13, he walked unknowingly into an exquisitely laid trap.
Not one, but two teams of assassins had rehearsed for the moment. The only ones Kim Jong Nam would see were female: two attractive women in their 20s who had been recruited locally. One of them, identified by police as Indonesian native Siti Aisyah, worked in a Kuala Lumpur massage parlor; the other, Doan Thi Houng, had moved from Vietnam to Malaysia to work in what authorities described vaguely as the "entertainment" industry.
Both would tell police that they were hired by a Korean man to perform "pranks," such as smearing baby oil on strangers, for a hidden-camera video show. For their service, each was promised $90 in cash and a shot at future TV stardom.
But on Feb. 13, the surprise prepared for Kim Jong Nam was VX, not baby oil. In a sequence that would be captured on security-camera video and later broadcast around the world, Kim Jong Nam was accosted as he checked in for a flight in the airport's departure lounge. A woman in a white sweatshirt is seen grabbing the North Korean's face from behind. Although the images are unclear, police think the second woman helped smear the oily liquid over the victim's cheeks.
At least four men - later identified by Malaysian officials as North Korean agents - are seen watching the attack and shadowing the visibly agitated Kim Jong Nam as he seeks help from police and an airport first-aid station. Minutes later, as the dying Kim is wheeled into an ambulance, the men slip through the departures gate to board flights out of the country.
The only ones who didn't escape were the women and the victim himself. Aisyah and Huong mysteriously avoided serious injury - perhaps, weapons experts speculate, because each handled harmless precursor chemicals that became toxic only when mixed, or perhaps because both women quickly washed their hands after the attack.
Both are seen quickly entering airport lavatories after the attack, behavior that prosecutors have cited in accusing the two women of being knowingly complicit in Kim Jong Nam's murder. The two women face court appearances later this month on charges of first-degree murder, a capital crime in Malaysia.
Kim Jong Nam, who quickly sought medical help after the attack, lost consciousness in the airport medical station and died in the ambulance, less than 20 minutes after the episode began.
It would take two autopsies and nearly two weeks to determine the name of the rare toxin that took his life. Malaysian investigators would conclude that the VX was smuggled into the country by North Korea, most likely in a commercial jetliner. It's unclear whether the toxin arrived ready-to-use or in a form that required mixing two harmless ingredients to create. In either case, the advantage for the assassins is that only a few drops are needed to kill, said a U.S. official with years of experience in chemical-weapons defense.
"Was it assembled in Malaysia? Not necessarily," said the official, who insisted on anonymity in discussing U.S. intelligence assessments of the North Korean threat. "A single three-ounce container that would fit in your carry-on luggage would hold far more than you'd ever need."
Until the Feb. 13 attack, hard evidence of Pyongyang's arsenal of toxins did not exist, at least in the public realm. But for at least two decades, U.S. intelligence assessments have concluded that North Korea possesses a sizable stockpile of chemicals weapons, with VX being one of many varieties.
A State Department report in 2001 found that North Korea was "already self-sufficient" in making all the necessary precursors for sarin and VX, as well as older weapons such as mustard gas. Drawing from an array of sources - from North Korean defectors and spies to satellite photos and electronic eavesdropping - U.S. agencies calculated the size of the country's chemical stockpile at between 2,500 and 5,000 tons. That's far larger than Syria's arsenal at its peak, and larger than any known to exist in the world, except for those built by the Soviet and U.S. militaries during the Cold War.
A parallel but reportedly much smaller program produces biological weapons, current and former U.S. intelligence officials think. Published Defense Intelligence Agency documents have described efforts underway to weaponize at least four pathogens: anthrax, plague, cholera and biological toxins, such as botulinum.
Work on chemical and biological programs began years before Pyongyang tested its first nuclear bomb, and U.S. analysts suspect that both were intended at first as a deterrent against foreign attacks. But while North Korea regularly boasts of its achievements in atomic energy and missiles, its chemical and biological weapons have always been kept carefully hidden, according to a study released jointly last month by the Johns Hopkins School of Advanced International Studies and the U.S. Korea Institute.
"North Korea has deliberately built its NBC [nuclear, biological chemical] infrastructures in extreme secrecy; undertaken camouflage, concealment and deception operations . . . and dispersed NBC facilities around the country," report author Joseph Bermudez Jr., a prominent expert on North Korean weapons systems, wrote in the report. "It is therefore probable that there are significant elements of the NBC programs and their infrastructures that are simply unknown outside the North Korean government."
U.S. and South Korean defense officials alike take the threat seriously, so much so that both governments inoculate their troops against exposure to anthrax bacteria and even the smallpox virus. Soldiers deployed along the border are issued gas masks and protective suits and put through occasional drills to prepare for the day when canisters of VX or sarin are fired across the border in North Korean rockets or artillery shells.
Any such attack would certainly prompt a massive retaliation. But Kim Jong Nam's assassination has forced U.S. officials to consider the possibility of a clandestine attack, one that might be more difficult to trace, or to defend against.
"With biological weapons, especially, there's an opportunity for covert attack with deniability, since attribution would be difficult," said Andrew Weber, former assistant secretary of defense for nuclear, chemical and biological weapons defense. Although U.S. officials are fixated on North Korea's nuclear advances, a nuclear attack "is not the most likely, or possibly even the most consequential," he said.
As Kim Jong Nam's assassination demonstrated, the delivery of such weapons can be easy - especially for spreading deadly pathogens, but also for toxic chemicals, he said. And any military response would be delayed for days or weeks while investigators attempted to find evidence that firmly pointed to a perpetrator.
"A chemical attack would be knowable, almost as soon as it happens," Weber said. "But Kim Jong Un is a brutal guy, and he may have no qualms against doing it. Or he may just miscalculate."
Kim Jong Un's plan to use VX to kill his half brother included extensive measures to ensure secrecy - so many, in fact, that some experts think the North Koreans wanted to keep its enemies ignorant about its use of the toxin, or at least unsure.
After Kim Jong Nam's death, Pyongyang requested the immediate return of his body, without an autopsy being performed. Malaysia refused, and soon afterward, local news media reported an attempt by unknown individuals to break into the morgue where the corpse was kept. The attempt failed, but in the weeks since, North Korea has insisted that the leader's half brother died of a heart attack and that any reports of chemical toxins were lies spread by outsiders.
Some longtime North Korea analysts are convinced that the killing was intended mostly as warning to other members of the Kim family who might be plotting Kim Jong Un's overthrow. The leader has a history of extreme brutality toward relatives whom he suspects of plotting against him. He may have seen Kim Jong Nam - a free-spoken man of leisure who enjoyed protected status in China and was widely reported to have intelligence contacts with several foreign governments - as a possible future choice by Beijing to replace him.
"It might have just been an expression of how much he hates traitors," said Joshua Pollack, a former government consultant on North Korean weapons programs and now editor of the journal Nonproliferation Review. "There's no doubt that VX was an unusual choice for an assassination. But I think it was probably chosen because they thought no one would look for it."
Other current and former U.S. officials say that North Korea would have calculated that the VX would be found eventually. According to these officials, Kim Jong Un's plan was to showcase his ability to strike with terrifying weapons, while also concealing the evidence to reduce the chances of retaliation.
"His message about VX was, 'We have it,' " said Terry, the former CIA analyst. "He knew they would eventually find it."
Whatever the motivation, the tactic worked, on nearly every level, North Korea experts say: A potential rival was eliminated. A capability to strike covertly, using one of the most fearsome chemical weapons ever designed, was amply demonstrated. And North Korea, while issuing denials that are widely seen as implausible, managed to get away with it, at least up until now.
"They carry out an attack and make people afraid, but then ensure that there's no evidence that can lead to real accountability," Pollack said. "For them, that's the sweet spot."