South Korea's impeached President Yoon Suk Yeol appeared in a Seoul court on Thursday for his first trial hearing on charges of insurrection in the country's first criminal prosecution of an incumbent leader.

South Korean police are formally building a case against impeached President Yoon Suk Yeol over accusations he obstructed the execution of an arrest warrant, a police spokesperson said on Friday. A South Korean court issued an arrest warrant for Yoon on December 31 in a criminal investigation accusing the suspended leader of insurrection over his martial law decree last year.

Impeached South Korean President Yoon Suk-yeol appeared before two courts on Thursday. His first stop at the Seoul Central District Court made him the first sitting president — he’s not yet been formally removed from office — to face criminal prosecution.