South Korea's impeached president found guilty in first of four trials: What you need to know

South Korea's beleaguered ex-president Yoon Suk Yeol has been found guilty of abuse of power, falsifying documents and obstructing justice when he tried and failed to impose martial law in the country in 2024. He has also been sentenced to five years in jail.

Yoon is facing three other trials for charges ranging from insurrection to violating campaign law.

The verdict comes more than a year after his short-lived decree threw South Korea into political turmoil, leaving it deeply divided.

Here's what to know about the key charges laid against Yoon.

On Friday, Yoon was found guilty of obstruction of justice by evading arrest; abuse of power by not convening a cabinet meeting before his martial law declaration; and falsifying official documents.

Prosecutors accused him of using state institutions "for personal purposes" to conceal wrongdoing and undermine constitutional checks and balances.

In January last year, it took some 3,000 police officers, over two attempts, to finally take Yoon into custody for questioning over the insurrection charge.

Yoon had mobilised a large group of security officers who formed a human wall inside his residence to block the arrest - a move that a special prosecutor investigating the charge said was unprecedented.

Yoon, meanwhile, argued the Corruption Investigation Office that attempted to arrest him lacked jurisdiction to investigate insurrection charges.

The chaos surrounding the arrest, and the earlier failed attempt, "demonstrated apparent lawlessness by Yoon, [his] conservative party, and South Korea's domestic security institutions", said Mason Richey, an associate professor at Seoul's Hankuk University of Foreign Studies.

"The obstruction of justice trial is a way to ensure accountability for these," he said.

Under South Korea's constitution, sitting presidents are immune from criminal persecution, except for on charges of insurrection and treason.

Yoon was charged on 26 January 2025. By then, parliament had voted to impeach him, but he was not yet removed from office.

Prosecutors allege that Yoon attempted to subvert the constitution by declaring martial law in the absence of war or any national emergency.

In particular, he's been charged over how he mobilised troops and police to seal off the National Assembly compound to prevent lawmakers from blocking his decree, and how he ordered the arrests of the National Assembly speaker and then-leaders of the main political parties.

Yoon had earlier claimed he declared martial law to protect the country from "anti-state" forces that sympathised with North Korea - but it soon became clear he was spurred by his own political troubles.

Prosecutors have sought the death penalty, describing Yoon as "unrepentant".

South Korea has not executed anyone since December 1997.

Former president Chun Doo-hwan, who ruled South Korea in the 1980s as a military dictator, was sentenced to death for leading an insurrection, though this was later reduced to life imprisonment. His ally and successor Roh Tae-woo was handed a lengthy jail term for his part in the insurrection. Both were eventually pardoned.

Prosecutors have argued, however, that Yoon's 2024 martial law attempt "tarnished the nation's dignity far more severely" than the military coup Chun and Roh staged in 1979.

"We all saw how he disrespected the courtroom, smirking and laughing amongst his lawyers during witness testimonies. That did not help his case at all," said law professor Lim Ji-bong.

Lim believes the judge will hand down a life sentence, though, so as to "avoid making Yoon a martyr". A death sentence carries political risk as it may further alienate Yoon's supporters and deepen chaos in the country, he said.

US-based lawyer and Korea expert Christopher Jumin Lee believes Yoon will ultimately be pardoned no matter what sentence he receives, as Chun and Roh were.

"It's a customary thing about Korean politics," Lee said. "Whatever the sentence, it's a symbolic acknowledgement of how severe the crime is."

Prosecutors have also alleged that Yoon tried to provoke North Korea into attacking the South so as to justify his martial law declaration.

In putting forward this charge, the prosecution relied on evidence found on former military intelligence chief Yeo In-hyung's phone that contained words suggesting potential provocations. They also cited a memo which appeared to push for a move to "create an unstable situation or seize an arising opportunity".

This trial, which opened on Monday, will look at whether Yoon ordered drone flights into the North to induce military conflict between the Koreas, among other things.

Yeo and Yoon's former defence minister Kim Yong-hyun have also been indicted on the same charge.

Yoon has also been accused of perjury, for when he testified during former prime minister Han Duck-soo's trial last year on charges of aiding the insurrection.

Prosecutors allege that Yoon falsely testified by claiming he had long planned to hold a cabinet meeting before declaring martial law. Investigators said Yoon had no such plan and only convened a meeting at Han's urging.

Apart from charges related to his martial law attempt, Yoon has also been indicted in a series of other cases.

He is among 33 people charged for allegedly obstructing an investigation into the death of a young marine officer in 2023, and for aiding the suspect in this case.

He has also been charged for meddling in the 2022 presidential elections and making false statements during his campaign.