SEOUL: Tuesday marks the start of South Korea's suspended president Yoon Suk Yeol's impeachment trial, which will determine the future of the former top prosecutor following his brief martial law order. Whether to support parliament's resolution to remove Yoon from office or reinstate him as president will be decided by South Korea's Constitutional Court. Let's takes a look at what we know: Armed troops stormed the National Assembly building on December 3 following Yoon's martial law decree, scaling fences, smashing windows and landing by helicopter. The country’s opposition-controlled parliament voted the decree down hours later, forcing Yoon to lift it. The court has 180 days from December 14, when it received the case, to rule on whether Yoon violated the constitution and the country’s martial law act. Yoon separately faces criminal charges of "insurrection" but has refused to be questioned by investigators and has resisted arrest. His lawyers have argued that the court must use the full 180 days — specifically to examine what "led to the declaration of martial law". The trial’s five hearings will proceed from January 14 to February 4 in Yoon’s absence if he does not attend. Yoon’s legal team says the former prosecutor remains inside his residence and may appear at one of the hearings, but that security issues must be resolved first. "Concerns about safety and potential incidents have arisen. Therefore, the president will not be able to attend the trial on January 14," lawyer Yoon Kab-keun said in a statement to . Former South Korean presidents Roh Moo-hyun and Park Geun-hye did not appear for their impeachment trials in 2004 and 2016-2017, respectively. Park was dismissed from office by the court in 2017, while Roh was able to serve a full five-year term after the court restored his powers. For Park, it took the court around 90 days to deliver its verdict, and around 60 days for Roh. But "for Yoon, the reasons for his impeachment are relatively straightforward," Yonsei Law School professor Lee Jong-soo told . Acting president Choi Sang-mok appointed two new justices to fill three vacancies on the Constitutional Court’s benches last month despite backlash from his ruling People Power Party. The decision has increased the likelihood of Yoon's impeachment being upheld — with at least six out of eight justices needed to back the decision. Among the eight, three are considered to be liberal while the others are categorised by local media as centrist or conservative. Two of the liberal justices, Lee Mi-son and Moon Hyung-bae have their terms slated to end on April 18. "There is a strong likelihood that a ruling will be reached before the terms of the two justices expire," said Yonsei's Lee. A new presidential election could be held within 60 days if the court dismisses Yoon. Opposition leader Lee Jae-myung is widely expected to win if this scenario unfolds. But Lee faces several trials over alleged corruption and other criminal charges. He was convicted of violating the election law in November and sentenced to a suspended prison term, and if the Supreme Court upholds the conviction before new polls, he will be barred from running. Legal experts say the verdict will likely be postponed until the end of Lee’s five-year term if he wins the presidency before the court’s ruling. According to South Korea’s constitution, a president "shall not be charged with a criminal offense" in office except for insurrection or treason. This clause is expected to be interpreted broadly to include criminal trials, allowing Lee to focus on his duties, Korea University law professor Kim Ha-yurl told . Recent polls show approval ratings for Yoon’s ruling party, which is defending the impeached president, have been rising as the crisis continues. A Gallup survey last week showed the People Power Party’s approval rating had risen to 34% from 24% three weeks before. Those who oppose a potential Lee presidency are rallying to support Yoon’s party. They believe "the only party capable of opposing the Democratic Party is the People Power Party," Park Sang-byung, a political commentator, told . If the Constitutional Court restores Yoon’s powers, political experts predict more turmoil. "There will likely be political retaliation (by the PPP)," Chae Jin-won of Humanitas College at Kyung Hee University told . Yoon’s supporters and allies have accused the court of bias. But the Constitutional Court is a neutral body "absolutely unaffected by public opinion" and "conducts fair judgements", court spokeswoman Cheon Jae-hyun told .