The morning of 13 February 2017 was like any other at Kuala Lumpur’s hectic international airport terminal so it would have been easy to miss a lone North Korean man, clad in a blue polo shirt and jeans, heading to check into his flight to Macau.

As he ambled past a column, a backpack slung over one shoulder, a woman approached him and wiped an oily substance on his face before disappearing, her unusual actions caught on CCTV. Moments later, another woman came from behind and covered his eyes with her hands. She then slid them down over his mouth, quickly apologised and walked away.

Less than 20 minutes later the man was dead, the victim of an assassination carried out with the nerve agent VX, one of the most deadly chemical weapons in the world.

The traveller was Kim Jong-nam, half brother of Kim Jong-un and one-time heir to the North Korean leadership who had since fallen out of favour with his powerful family. As the attack was carried out, in scenes that would not be out of place in a James Bond film, at least four North Korean agents were hiding nearby to witness the public killing and ready with a back-up plan if anything went wrong.

Doan Thi Huong is escorted by Malaysian police out of the high court in Shah Alam on 1 April. Photograph: AFP Contributor#AFP/AFP/Getty Images

In the hours after the attack, those agents passed through immigration checkpoints and boarded flights out of the country, accompanied by a North Korean diplomat. Their flight routes back to Pyongyang were carefully calculated to avoid countries that may ground their planes and arrest the men.

“The reason to do it publicly is to leave a calling card, to show the world that Kim Jong-un is not afraid to use a weapon of mass destruction at a crowded international airport,” said Vipin Narang, a politics professor at the Massachusetts Institute of Technology.

Indeed, the people who would find themselves on trial for the murder were not agents of the North Korean state but two former escorts, Siti Aisyah, from Indonesia, and Doan Thi Huong, from Vietnam. The women, according to their testimonies, had been unknowingly groomed as killers by North Korean agents in the months previous. It was Siti and Doan who had smeared the substance on Kim Jong-nam’s face, later both telling Malaysian police they thought they were carrying out a prank for a Japanese YouTube show.

In March, all charges were dropped against Siti and Doan found herself the sole person accused of murder. On Monday, she was offered a deal – accept a lower charge of causing hurt with a dangerous weapon and face 10 years in prison, instead of a mandatory sentence of death by hanging if found guilty of murder. She agreed, saying only “I’m happy” in court. Doan was sentenced to three years and four months but her legal team said that with usual sentence reductions, she would be released in May.

Death and a diplomatic crisis

The killing of Kim Jong-nam on foreign soil caused a major diplomatic crisis between North Korea and Malaysia, with Malaysia expelling the North Korean ambassador, refusing to release Kim Jong-nam’s body to Pyongyang and demanding three North Koreans hiding in the embassy come in for questioning by the police, to which North Korea responded by holding hostage all Malaysians in North Korea.

However, in the two years since the murder, behind-the-scenes diplomacy has taken over and appears to have significantly influenced how events have unfolded in the courtroom.

After a judge ruled that both Siti and Doan should testify, a full-blown diplomatic campaign began in Indonesia. President Jokowi met the Malaysian prime minister, Mahathir Mohamad, twice in 2018 to press for Siti’s release. It proved effective; in an order signed by the attorney general that cited the “good relations” between Malaysia and Indonesia, Siti was acquitted in March.

Siti Aisyah smiles as she arrives in Jakarta from Malaysia. Photograph: Mast Irham/EPA

But it is not just Indonesia the Malaysian government has been accused of appeasing. The decision to let Siti go and allow Doan to plead guilty to a lesser charge has led to accusations that the Malaysian government wanted to be done with the trial because it was diplomatically inconvenient. Before the assassination, North Korea and Malaysia had four decades of good diplomatic and trade ties, which were strengthened under Mahathir the first time he was in power in the 1990s. It is believed that Mahathir, who took power again in May last year, was keen to recover the relationship.

“What is now clear is that the Malaysian government considered the recovery of the relationship between Pyongyang and Kuala Lumpur to be more important than justice for the assassination of Kim Jong-nam,” said Dr Nam Sung-wook, a professor at Korea University who previously worked in South Korea’s Intelligence agency. “Kim Jong-un’s status is on the rise now he is meeting with the US president and the Vietnamese prime minister and leaders in the region, and Malaysia also wants to be part of this conversation.”

A UN report, released in March, which investigated violations of the UN arms embargo and financial sanctions against North Korea, named Malaysia as one of the key culprits, singling out several Malaysian companies and senior business figures who had benefited from clandestine deals.

“Some members of the ruling party are deeply involved in financial networks that are partly North Korean so the government clearly don’t want to alienate North Korea with this trial dragging on; it will cost them money and embarrassment and perhaps even international sanctions,” said Dr Remco Breuker, an expert on North Korea at Leiden University.

‘Washing away North Korea’s sins’

From his birth in 1971, as the eldest son of Kim Jong-il, Kim Jong-nam was slated to rule North Korea. But after being sent to a Swiss boarding school, he developed a taste for luxury items and a decadent lifestyle. In 2001, in an incident seen to embarrass his family, Kim Jong-nam was arrested trying to enter Japan to visit Tokyo Disneyland. He later spoke publicly about his belief in political and economic reform for North Korea.

But he was still seen as a potential rival to his younger brother, Kim Jong-un. There were at least two botched assassination attempts against him in 2010 and 2012 and Kim Jong-un was rumoured to have issued a standing order to kill his older brother.

There were at least two previous attempts on Kim Jong-nam’s life.

Photograph: Shizuo Kambayashi/AP

His eventual murder was seen to be a warning shot aimed at high-level North Korean defectors such as Thae Yong-ho, the former North Korean ambassador to Great Britain, who had recently spoken out publicly. It proved effective; in the aftermath Thae Yong-ho and several others cancelled all public appearances and have kept a low profile since.

The apparent decision by North Korea to recruit and groom two innocent women to carry out the killing appeared to be an attempt by Kim Jong-un to avoid a repeat of the Rangoon bombing incident in Burma in 1983, when two North Korean officers who attempted to publicly assassinate the South Korean president, Chun Doo-hwan, were captured and put on trial.

Instead,the real perpetrators in Pyongyang, who both the US and South Korea have definitively concluded are guilty of orchestrating the crime, have faced no retribution for the assassination.

“You’d expect ramifications for North Korea, but given the welcome Kim Jong-un received when he went to Singapore and then Vietnam for the nuclear summits with Trump, no, I don’t think so,” said Breuker. “The international community are very good at washing away North Korea’s sins for them.”

He added: “I don’t think North Korea cared either way whether these women were released or executed, for them this was over long ago. North Korea hasn’t been indicted, the people who were connected to the killing left the country in the immediate aftermath, so they got away scot-free. As the assassination and this trial have shown, they can act with near total impunity and will probably do so again.”