Otto Warmbier death: What killed the US student who stole a poster in North Korea?

Otto Warmbier, the 22-year-old college student who returned to the United States last week after 17 months of detention in North Korea, died on Monday.

Warmbier had suffered severe brain damage during his captivity and spent more than a year in coma. He was convicted of stealing a propaganda banner and sentenced to 15 years of hard labour in a North Korean prison, after a trial held in March 2016.

North Korean authorities said he fell ill from botulism soon after his trial and went into a coma after taking a sleeping pill. But doctors in the USA, who treated him following his arrival from North Korea, have dismissed the claim.

Politicians and celebrities in the US, including President Donald Trump, have accused North Korea of torturing and "murdering" Warmbier.

The 'serious' crime

Warmbier, who had been in North Korea as a tourist with a travelling group organised by Chinese company early last year, was accused of stealing a propaganda poster hanging from the wall of the hotel he was staying in.

In a confession made at a news conference in February 2016, Warmbier said a friend of his mother offered him a used car to steal the poster. However, the youth's father Fred Warmbier said the story was nonsensical and the confession was a forced one.

In most countries in a world, stealing a poster from your hotel doesn't even count as a crime. But as we have painfully learned, in a totalitarian regime it could get you 15 years of imprisonment. And in this case, it cost a bright young student his life.

What caused the death?

During his confession in February, Warmbier had showed no signs of injury or illness but by March, he slipped into a coma. Doctors in the US have denied North Korea's claim that thecoma was induced by botulism and sleeping pills, as tests did not reveal any evidence of this.

Neurologists found out that the youth had suffered extensive loss of brain tissue but the cause for this condition remains unknown. However, the pattern of the brain damage suggests a cardiopulmonary arrest.

The most common theory is that Warmbier was repeatedly beaten and torutured while in custody till he suffered a cardiopulmonary seizure. But his body displayed no obvious evidence physical trauma or bone fractures. Another possible explanation is that Warmbier was heavily medicated, causing irreversible brain damage.

Either way, the incident throws light on the brutal and inhuman abuse and torture methods put into use in North Korean prisons. The youth's father has accused North Korea of abusing his son. In a statement released this week, the Warmbier family said the North Korean government subjected their son to "awful torturous mistreatment" which led to his death.

We have already learned about the unimaginable torture methods deployed in North Korean prisons from some of the survivors. By sending Warmbier back to the US in a vegetative state, Kim Jong-un has proved that not only the leaders of countries that oppose him but also its ordinary citizens can expect no mercy from his regime.

• Otto Warmbier