President Yoon Suk-yeol, who declared martial law on December 3 last year, is using his power, legal knowledge, and supporters to escape punishment. He is using all sorts of “legal techniques” to block the Corruption Investigation Office for High-ranking Officials (CIO)’s investigation into his rebellion and the Constitutional Court‘s impeachment trial. Critics say that the president, who is supposed to uphold the constitution, is shaking up the criminal and judicial systems, and is thus entering the swamp of impeachment by himself.

So far, Yoon has used a variety of “defense tactics,” including invoking his right to remain silent, refusing to sign and seal the statements, refusing to cooperate with the investigation, seeking the writ of habeas corpus, requesting a postponement of the trial date, and filing charges against the person in charge of the investigation.

Yoon postponed the second round of interrogation on the morning of January 16, citing “health reasons,” and then refused to submit to the afternoon interrogation, saying, “There is nothing more to be investigated because I told them enough yesterday.” Prior to his arrest by the CIO the day before, Yoon had been “hanging tough” at the presidential residence under the protection of the Presidential Security Service.

Yoon‘s defense filed charges of insurrection against Oh Dong-woon, the head of the CIO, and Woo Jong-soo, the head of the National Office of Investigation, with the Seoul Central District Prosecutors‘ Office. They argued that the CIO and police investigators broke into the presidential residence, which is a military secret under the Military Confidential Protection Act, and that "it constitutes a rebellion that excludes state power, and in the process, they committed a myriad of crimes, including obstructing the execution of special public affairs and the exercise of rights to abuse authority and violating the Military Confidential Protection Act."

Yoon refused to make any statements during an eight-hour, 20-minute interrogation at the CIO office the previous day. After completing the investigation, he neither read nor signed the protocol of examination of a suspect. Reports without signatures or seals have no evidentiary value in a future trial. On the previous evening, he filed a habeas corpus petition with the Seoul Central District Court to determine whether his arrest was lawful. Yoon argues that the CIO lacks jurisdiction to investigate insurrection, and that the warrant issued by the Seoul Western District Court, not the Seoul Central District Court, is illegal.

Yoon remained silent throughout the CIO’s investigation the day before, but he asked for the second hearing of the impeachment trial, which was held on the day, to be postponed, citing the CIO’s investigation. He also argued that the Constitutional Court would be violating his right to be present if it held the hearing while he was in detention, but the court refused to accept it.

Yoon also dragged his feet by refusing to receive a request for an answer sent by the Constitutional Court for a week from December 16 last year. When the Constitutional Court assumed that he had received the documents and accelerated the pace of the trial by scheduling five rounds of hearings in one go, Yoon reacted by calling it “limiting his defense rights” and “biased.” Yoon was absent in the first hearing, saying he feared for his safety as the CIO attempted to execute a warrant for his arrest.

Yoon‘s lawyers have raised the issue at every stage of the investigation and impeachment procedure, insisting on “guaranteeing the suspect’s right to defense.” “Any evidence obtained in an illegal investigation loses its evidentiary value,” Yoon’s lawyer Yoon Gap-geun said in a statement released on January 13.

However, Yoon criticized this behavior by powerful people when he was a prosecutor. “Those in power often take issue with trivial procedures and the process of obtaining evidence,” Yoon said in his farewell speech as the prosecutor general in March 2021.

While emphasizing the “rule of law,” Yoon has been using off-the-record publicity to rally his hardline supporters to put pressure on the investigation and trial.

“I will fight with you until the end,” he wrote to supporters gathered outside his presidential residence on January 1. In a video and handwritten letter released shortly after his arrest, he claimed that “all laws in this country have been broken” and that “there is too much evidence of election frauds.” In fact, Yoon‘s supporters have been rallying outside the Government Complex in Gwacheon, where the CIO office is located, and the Seoul Detention Center where he is detained.

The obstruction of the investigation and impeachment trial is likely to work against Yoon.

Han Sang-hee, a professor at Konkuk University's Graduate School of Law, said, “He is using the suspect’s right to defend himself as a means for his own political purposes. While in the presidential position, he has denied the criminal and judicial system itself and has undermined the authority of national law by sending out messages to unite his supporters.”