South Korea’s former president Yoon Suk Yeol denied he had committed insurrection, as the impeached ex-leader appeared in court for the opening of his criminal trial over his martial law declaration.

Yoon was formally stripped of his presidential powers this month, after being impeached and suspended by lawmakers over his December 3 attempt to subvert civilian rule, which saw armed soldiers deployed to parliament.

He became South Korea’s first sitting head of state to be arrested in January in connection to the criminal case against him, although he was later released on procedural grounds.

Yoon attended the trial at Seoul Central District Court and was asked by the justices to state his name, date of birth and other personal information.

The former president has denied the charges against him and took to the stand on  Monday to defend himself.