Kim Jong Un's half brother was assassinated with nerve poison one year ago — here's how it went down and the remaining unsolved mysteries

• Kim Jong Un's elder half-brother was assassinated at a Malaysian airport on February 13, 2017.
• One year later, many questions surrounding Kim Jong Nam's death remain unanswered.

It's been one year since the half-brother of North Korean leader Kim Jong Un was assassinated at a Malaysian airport — but the much of the case remains a mystery.

Kim Jong Nam was killed after two women rubbed a lethal nerve agent called VX on his face at Kuala Lumpur International Airport on February 13, 2017.

Both women, who have been charged with murder, have consistently maintained their innocence, claiming that they thought they were participating in a prank for a TV show. Four men have been charged as well, but are still on the run.

The murder trial started last October and is scheduled to finish on March 22, 2018.

Here's what we know about the assassination — and what we still don't.

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This is Kim Jong Nam. He was the eldest son of North Korean supreme leader Kim Jong Il and one of his mistresses, and was once considered a potential successor.

Kim Jong Un and his siblings — including Kim Yo Jong, whom he sent to the Pyeongchang Olympics— are the children of a different mistress, a former dancer named Ko Young Hui.

Here's video footage of the assassination, shown in video footage obtained by the Japanese TV channel Fuji Television, and annotated by the UK's Channel 5 News.

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The women accused of killing Kim Jong Nam have said they thought they were taking part in a prank for a TV show.

The suspected assassins — 25-year-old Indonesian Siti Aisyah and 29-year-old Vietnamese Doan Thi Huong — have both pleaded not guilty and said they thought they were taking part in a prank for a hidden-camera reality TV show.

Aisyah was so convinced of her innocence that she thought that her arrest and subsequent imprisonment were part of the prank, the acting Indonesian ambassador in Malaysia at the time told GQ magazine.

Andreano Erwin, the ambassador, told GQ: "The first time we visited her, she kept asking when she could leave the jail. The second, she complained that she still hadn't been paid for the last prank. The third time, she accused us of being part of the prank.

"The fourth time, we showed her a newspaper proving Kim Jong-nam had died. When she saw it, she started to cry."

Doan was wearing a white shirt emblazoned with the word "LOL" at the time. The shirt's designer said shortly after the assassination that he "thought she looked very stylish."