Seoul's Constitutional Court announced an additional hearing in the impeachment trial of South Korean President Yoon Suk-yeol on Tuesday, after the last designated hearing concluded on Thursday.

"We will conduct an evidence review for the records that were admitted as evidence but have not yet been examined," said Moon Hyung-bae, acting chief justice of the Constitutional Court, according to Yonhap News Agency.

Moon said the National Assembly and Yoon will both be given two hours to summarize arguments and present key points of their documentary evidence.

According to the original schedule, Thursday was the eighth and final designated hearing date for Yoon's impeachment trial.

During Thursday's hearing, Yoon's legal team accused the Constitutional Court of unlawful proceedings, warning of serious action if the impeachment trial continued in the current manner. They did not elaborate on what that action might be.

Yoon's lawyer Yun Gap-geun said the court violated the law and is conducting an unlawful and unfair trial.

"What is more important than a quick decision is a prompt, fair, accurate and politically neutral trial that the public can trust, as this is what gives meaning to the existence of the Constitutional Court," said Yun.

The team requested once again to call impeached Prime Minister Han Duck-soo as a witness.

Yoon was impeached by the National Assembly on Dec 14 over his short-lived martial law decree earlier in the month. He has since been suspended from office, and was arrested on Jan 15.

Witnesses questioned in the eighth hearing were the Chief of the National Intelligence Service Cho Tae-yong, the former chief of the Seoul Metropolitan Police Agency Kim Bong-sik, and the Head of the First Security Command of the Capital Defense Command Cho Sung-hyun.

The National Assembly's legal team — which is serving as a prosecutor in the impeachment trial — said the acts by Yoon's side undermined the court's credibility.

Song Doo-hwan, an attorney from the National Assembly's impeachment committee, said the facts regarding the trial have been clarified to a considerable degree, and he believes it is the right time for a constitutional assessment of whether the martial law declaration and the actions that followed were unconstitutional and illegal.

The timing of the verdict depends on whether the court accepts additional witnesses requested by Yoon's side and schedules more hearings, said Cho Hee-kyoung, a law professor at Hongik University in Seoul.

If no further hearings are held, a verdict could come as early as the end of this month or early March, she told China Daily.

The Constitutional Court said it would decide on Friday whether to admit additional witnesses.

"If there are more hearing dates, then the verdict will be pushed back accordingly," Cho said.

In the previous presidential impeachment trials in South Korea, the ruling was delivered in 91 days for former president Park Geun-hye and 63 days for former president Roh Moo-hyun. Those decisions were announced about two weeks after oral arguments ended.

Insurrection charges

Local media also reported that the first preliminary hearing for Yoon's criminal case on charges of leading an insurrection is scheduled for Thursday.

A simultaneous court hearing will take place to review Yoon's request to cancel his detention.

Currently, Yoon is only indicted on charges of insurrection as he is a sitting president, but he will lose presidential immunity and will likely be charged with additional crimes once the impeachment motion is upheld by the court, said Cho.

"Yoon will be in his element in the criminal trial and will use every tactic he can to challenge the indictment and the court and the judges and to draw out the proceedings," said Cho, who expects a prolonged criminal trial.

A survey released on Thursday showed that 58 percent of South Korean residents polled agreed the Constitutional Court should uphold Yoon's impeachment, while 38 percent said it should be dismissed.

The number of respondents who said Yoon should be removed from office through impeachment increased by 3 percentage points from the previous week, while 54 percent of respondents said they trusted the process of the impeachment trial, up 2 percentage points from last week.

The latest National Barometer Survey was jointly conducted by four research institutes from Monday to Wednesday, polling 1,001 South Korean residents aged over 18.

The suspended president's supporters have gathered outside the court throughout his weekslong trial.

Yoon's legal team announced it would officially launch a "citizen defense team" of supporters seeking to "save" him and have him reinstated. According to the lawyers, 15,000 people have applied to join the team.

Agencies contributed to this story.

kelly@chinadailyapac.com