Yoon Suk Yeol’s attempt to impose martial law was to thwart a “legislative dictatorship” by the opposition-controlled parliament, the ousted South Korean leader’s lawyer has said.
Mr Yoon faces life imprisonment or the death penalty for charges of insurrection after his arrest last month.
The 64-year-old former prosecutor is the country’s first sitting president to stand trial in a criminal case.
Criminal proceedings at Seoul’s Central District Court on Thursday morning lasted just over an hour.
Mr Yoon attended the hearing but did not speak.
There was heavy security around the building, with 3,200 police personnel mobilised on site, Yonhap news agency reported.
Supporters swarmed outside the courthouse – Ahn Young-joon/AP Photo
Much of Mr Yoon’s impeachment trial centres on whether he violated the constitution by declaring martial law, which is reserved for national emergencies or times of war.
His decree only lasted around six hours as the opposition-led parliament defied troops to vote it down.
Prosecutors accused the suspended president of being the “ringleader of an insurrection”.
They argued against releasing him from the detention facility where he has been held since mid-January, saying Mr Yoon could try to “influence or persuade those involved in the case”.
Addressing the court, Kim Hong-il, Mr Yoon’s lawyer, condemned the “illegal probe” against his client, arguing the “investigating body has no jurisdiction”.
“The declaration of martial law was not intended to paralyse the state,” Mr Kim said.
He claimed it was instead meant to “alert the public to the national crisis caused by the legislative dictatorship of the dominant opposition party, which had crippled the administration”.
“The judiciary must serve as the stabilising force,” he told the court’s three judges and warned he was “witnessing a reality where illegality compounds illegality”.
South Korea’s Constitutional Court is separately deliberating whether to formally remove Mr Yoon from office following his impeachment by parliament in December.
His 10th session in that case is scheduled for 3pm Thursday afternoon (6am GMT), a few hours after the hearing in his criminal trial.
Han Duck-soo, who was also impeached as acting president, and Hong Jang-won, the former senior intelligence official, were called to testify at that hearing.
Cho Ji-ho, the head of South Korea’s National Police Agency, who is also on trial on insurrection charges, has been called as a witness.
It is not clear whether the impeachment hearing will be his last before the Constitutional Court’s eight judges deliberate – a process that could take up to a fortnight or even longer.
If Mr Yoon is removed from office, the country must hold fresh presidential elections within 60 days.
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