What is the ”important decision” that South Korean President Yoon's lawyer hinted at during his impeachment trial?

The impeachment trial to determine whether the impeachment of South Korean President Yoon Seok-yeol is appropriate ended on the 13th of this month as originally scheduled. However, the Constitutional Court extended the hearing period.
The Korean newspaper Chosun Ilbo reported, "The Constitutional Court set the 18th as an additional hearing date in response to the recent rise in 'hasty' trials.
Prior to this, Yoon Kap-geun, a lawyer for Mr. Yoon's legal team, protested to the Constitutional Court during the eighth hearing on the 13th, saying, "The court is continuing to conduct illegal and unfair trials."
"If the trial continues in a serious manner, the defense team will be forced to make a serious decision," he said. What does "serious decision" mean? Yoon declared "emergency martial law" in December last year. Emergency martial law is a state of emergency defined in the South Korean Constitution.
A type of martial law that is issued by the president in times of war, emergency, or other military emergency, or to maintain public order. The military takes control of administrative and judicial functions, and freedom of speech and publishing is restricted.
・Freedom of association can also be restricted. This was the first time that martial law had been declared since democratization in 1987. Following the declaration, armed martial law soldiers broke the windows and stormed into the National Diet building.
In a situation reminiscent of the military regime, many citizens gathered in front of the National Diet, chanting slogans against martial law and surrounding military vehicles, causing chaos.
However, if a majority of the members of the National Assembly request the lifting of martial law, the President must comply with this request, and immediately after the declaration, a plenary session of the National Assembly is held and all the members present vote to lift the state of martial law.
In favor of lifting it, Yoon lifted the emergency martial law in just six hours. Although the "emergency martial law" that Yoon suddenly declared was lifted early, it caused confusion in Korean society, and the unstable political situation continues to this day.
Opposition parties including the Democratic Party of Korea have filed a motion to impeach Yoon in the National Assembly, accusing him of violating the constitution by "attempting to disrupt the constitutional order and committing an internal rebellion aimed at permanently seizing power."
The bill was put to a vote in December last year and passed with 204 votes in favor and 85 against. As a result, Yoon was suspended from his duties, and Deputy Prime Minister and Minister of Strategy and Finance Choi Sang-mok is now in charge of the presidency.
The bill passed the Constitutional Court's six-month decision on whether to impeach or reinstate Yoon. If he is impeached, a presidential election will be held within 60 days.
The Constitutional Court has been holding oral arguments since last month, and Yoon has personally attended to protest the injustice of the impeachment. The eighth oral argument in the impeachment trial was held on the 13th.
Amid criticism, all of the arguments that were originally scheduled were completed on the same day. Yoon's defense team was dissatisfied with the fact that the eight previous arguments had contained a large amount of testimony that was unfavorable to Yoon, and decided to postpone the eighth argument on the 13th.
During the argument, Yoon Kap-geun, a lawyer for Yoon's defense team, requested that Prime Minister Han Deok-soo be called as a witness. Yoon Kap-geun said, "(Prime Minister Han) has no say in who is responsible for the cause of this 'emergency martial law.'"
"I know better than you," he said. Yoon's legal team had requested to call Han as a witness on the 11th, but the Constitutional Court had rejected the request.
"I applied to be a key witness, but it was rejected because I was not relevant. There was no specific explanation, so I don't know why I was not relevant," he said.
The Constitutional Court decided to extend the hearing date, which was originally scheduled to end on the 13th, and approved the defense team's request to resubmit witnesses.
The prime minister and two others have been appointed as witnesses for the impeachment trial. Han will appear as a witness for Yoon at the 10th hearing on the 29th. Meanwhile, lawyer Yoon Kap-geun said at the 8th hearing on the 13th that the Constitutional Court
"They are continuing to conduct illegal and unfair trials," he said, adding, "If the trials continue like this, the defense team will have no choice but to make a major decision."
The Korean media has taken notice of his remarks. It has been reported that the "serious decision" may refer to the resignation of the entire defense team. If the defense team resigns, it will take a considerable amount of time to form a new defense team.
The progress of the impeachment trial of Mr. Yoon, which has been criticized as being hasty, began in early to mid-March.
Regardless of whether Yoon is removed from office or not, the Constitutional Court's decision will have a major impact, and Yoon's side is considering whether he will step down of his own accord before the Constitutional Court's ruling.
There is a view that he is trying to make a choice. If he resigns, public sympathy for the president will increase, and the subsequent presidential election will be favorable for the ruling People Power Party.
It has been pointed out that there may be political calculations at work, with the expectation that the ruling will be successful. Some have speculated that the resignation of the defense team is a tactic to buy time in order to delay the Constitutional Court's decision, but
According to the South Korean newspaper Dong-A Ilbo, a source from the legal team said, "We are considering two or three options for this 'major decision,' including the resignation of the legal team, but we are not considering the possibility of (the president) stepping down."
He rejected that view.