Moon Hyung-bae, second from right, acting chief justice of the Constitutional Court, and other justices arrive for the second hearing in President Yoon Suk Yeol's impeachment trial at the court in Jongno District, Seoul, Thursday. Joint Press Corps

The Constitutional Court's second hearing on President Yoon Suk Yeol's impeachment proceeded without his attendance on Thursday, as the detained president failed to appear.

Yoon, who skipped the first hearing on Tuesday citing concerns about potential detention if he left his residence, was absent from the second hearing after those fears materialized.

Investigators executed a detention warrant against him on Wednesday morning, allowing them to hold him for questioning for up to 48 hours.

The suspended president faces impeachment trials at the Constitutional Court for his brief imposition of martial law on Dec. 3 last year. He also faces a separate criminal probe on charges of treason and abuse of power.

Unlike the first hearing, which lasted only four minutes due to Yoon's absence, Thursday's hearing proceeded in accordance with due process. Under relevant laws, the court can continue deliberations from the second hearing and onward even if the president fails to attend.

The National Assembly's impeachment investigation committee, acting as prosecutors in the trial, argued that Yoon should be ousted swiftly as he is unfit to serve as president, citing his lack of willingness to uphold constitutional order.

They also claimed that his martial law declaration failed to comply with legal requirements or procedures.

"The martial law decree, which labeled political opponents as anti-state forces and attempted to eliminate them, amounts to abolishing the liberal democratic order and declaring dictatorship," lawyer Lee Jin-han, legal representative of the Assembly, said.

Members of the National Assembly's impeachment investigation committee, led by Rep. Jung Chung-rae of the main opposition Democratic Party of Korea, center, arrives at the Constitutional Court in Seoul for the second hearing in President Yoon Suk Yeol's impeachment trial, Thursday. Yonhap

Yoon's defense team claimed that the martial law imposition was a legitimate exercise of presidential authority and that the emergency military rule, which lasted only six hours due to parliamentary pushback, did not constitute insurrection.

Yoon has defended his actions in multiple public statements before and after his arrest, asserting that they were intended as a warning to opposition parties, which he accused of wielding excessive legislative power.

In a written statement submitted to the court the previous day, Yoon's lawyers claimed that the controversial first clause of the martial law decree — banning all political activities, including those of the National Assembly, local governments and political parties — was the result of an "error."

This clause has come under scrutiny because, while the Constitution allows "special measures" regarding freedom of the press, executive authority and the judiciary during martial law, it does not permit restrictions on legislative activities.

Yoon's legal team explained that former Defense Minister Kim Yong-hyun, who drafted the decree, mistakenly copied those phrases from earlier martial law declarations issued during the military regime of the 1980s, when the president had the authority to disband the legislative body.

President Yoon Suk Yeol is taken to the Seoul Detention Center in Uiwang, Gyeonggi Province, Wednesday night, following hours of questioning over his martial law imposition at the Corruption Investigation Office for High-ranking Officials in Gwacheon, Gyeonggi Province. Yonhap

Although a detainee can technically attend a hearing with the cooperation of investigators, Yoon apparently did not intend to do so for Thursday's hearing.

Hours after he was detained for questioning at the Corruption Investigation Office for High-Ranking Officials (CIO) in Gwacheon, Gyeonggi Province, his lawyers requested a postponement of the hearing.

They argued that, given Yoon's late-night questioning, it would be difficult for him to attend the court proceedings the following day. They also claimed that holding a hearing while the respondent is detained would infringe upon the president's rights to attend the proceedings.

However, the court rejected the request.

"After deliberation, the court decided not to accept the request for a date change. The decision was made through discussions among all members of the bench," court spokesperson Chun Jae-hyun said at a briefing on Thursday morning.

The court's decision appears to reflect its intention to proceed swiftly with the trials, as Yoon's legal team has been apparently employing various tactics to delay the procedures.

During the preparatory hearing stage, before formal hearings began, Yoon's legal team refused to accept court documents for over two weeks. Once formal hearings started, they filed multiple objections to the court, including one demanding the removal of Justice Jung Gye-sun for her perceived left-leaning stance.

The Constitutional Court has about five months to decide whether to formally remove Yoon from office, in order to meet the 180-day deadline following the National Assembly's decision to impeach him on Dec. 14.

The court said it will schedule three more hearings for Feb. 6, 11 and 13, in addition to the planned hearings for next Tuesday, Thursday and Feb. 4.