SEOUL (Reuters) - The South Korean court that will rule on the impeachment of President Park Geun-hye has only one precedent and little in the law books to go by, and several legal experts said it will have wide discretion in deciding if she is fit to remain in office.
Seven of nine experts interviewed by Reuters said they believed the Constitutional Court's yardstick in deciding whether Park should remain in office would be less than the "beyond a reasonable doubt" standard for criminal trials, making it more difficult for her to win the case.
South Korean law does not specify the standard needed by the Constitutional Court to reach a ruling. It calls for criminal procedural law to be applied during an impeachment trial "at a level that does not clash with the nature of a constitutional trial".
Experts say this means that the Constitutional Court has discretion on deciding which part of criminal procedure it will apply, including whether to use a rigorous level of proof, a lower standard, or apply a rigorous standard for some deliberations and a lower standard for others.
Two experts, however, said a high standard would be needed to establish grounds for upholding impeachment.
Park, 64, was impeached by parliament last month over an influence peddling scandal. If the nine-judge Constitutional Court rules that she did allow a friend to have influence over state affairs, as alleged, and that it was an impeachable offence, she will be ousted, making her South Korea's first democratically elected leader to be forced from office.
"This is not a criminal trial, it's a constitutional trial deciding whether a president is no longer fit to carry out presidential duties," said Noh Hee-bum, a lawyer who worked as a Constitutional Court research judge from 1998 to 2015.
"Although it's not expressly stipulated in law, it is the prevailing view that the level of proof is not as severe."
That, some experts said, would make it more difficult for Park.
"The common view, a lower burden of proof, is comparatively unfavourable to Park than a higher burden of proof would be," said Koh Moon-hyun, a professor at the Soongsil University College of Law.
Park has repeatedly denied any wrongdoing and her lawyers have argued that the case should be thrown out.
"In an impeachment proceeding, proof beyond a reasonable doubt is needed," her lawyer, Lee Joong-hwan, said in court on Tuesday, citing a publication by the research institute attached to the Constitutional Court.
"We can see that this means a rigorous level of proof is needed based on evidentiary principles of criminal procedure," he said.
The parliament's impeachment committee and its legal counsel, who are the prosecutors in the case, could not immediately be reached for comment.
Two sessions of the trial have been held this week and Park did not attend, as expected. Lee said he believes she will not appear, barring special circumstances. The court can take several months to deliver a ruling.
Park is accused of violating her constitutional duty by allowing her friend Choi Soon-sil to wield undue influence over state affairs and colluding with her to pressure big businesses into making contributions to foundations and enterprises backed by Choi.
Choi is in custody as she undergoes criminal trial for abuse of power and fraud, while her daughter, 20-year-old equestrian competitor Chung Yoo-ra, has been detained by police in Denmark and faces extradition proceedings after being charged with "committing economic crime" in South Korea.
Both have denied any wrongdoing.
In South Korea's only previous presidential impeachment, the Constitutional Court overturned a 2004 parliamentary impeachment of then-President Roh Moo-hyun.
The 2004 case mainly involved Roh's public comments supporting a political party as an election loomed, which the court said violated a law requiring government officials to be politically neutral but was not serious enough to warrant impeachment. The judges voted 6 to 3 to overturn that motion.
In that decision, the court cited five examples of grounds for impeachment, and experts said the impeachment committee is likely to argue in favour of at least three of them in Park's case - "acts of corruption," "harming the national interest" and "violating the people's basic rights".
As the only precedent, the Constitutional Court is expected to closely adhere to the logic of the 2004 ruling - especially on what constitutes grounds for impeachment, experts said.
Lee In-ho, a professor at Chung-Ang University School of Law, said although the level of proof required to convince the judges was not expressly spelled out in law, a high standard would be needed.
"In 2004, the Constitutional Court ruled that if facts do not verify that the president directed, abetted or otherwise unlawfully participated in the act in question, it is not grounds for impeachment," Lee said. "I believe the judges will decide that a rigorous level of proof similar to a criminal trial is needed."
For the impeachment to stand, at least six of the nine judges must rule in favour of it.
The terms of two of them are set to expire soon - one on Jan. 31 and the other on March 13 - potentially leaving just seven judges, the minimum required. If the case goes past March 13, that could work in Park's favour because the number of judges needed to uphold impeachment remains at six.
Unlike in 2004, each judge's decision will be made public.
($1 = 1,206.9000 won)
Editing by Tony Munroe and Raju Gopalakrishnan