The three-judge panel had already held two preliminary hearings with only prosecutors and Ms. Park’s lawyers attending. With the session on Tuesday, where Ms. Park’s appearance was mandatory, the formal legal arguments officially began over the criminal charges she faced, including bribery, coercion, abuse of office and illegal leaking of government secrets.

“It is an unfortunate scene in our history for a former president to be arrested and stand trial,” Lee Won-seok, the lead prosecutor, said on Tuesday. “But we should establish the rule of law by punishing her illegal activities.”

Ms. Park said “yes” when the judge asked whether she denied all charges against her.

It remained unclear when the court would rule on her case.

Hers is the biggest court trial since 1996, when the former military dictator Chun Doo-hwan was sentenced to death and his friend and successor, Roh Tae-woo, was sentenced to 22 and a half years in prison on bribery, mutiny and sedition charges. (Their sentences were later reduced, and they were pardoned and released in 1997.)

Ms. Park was tried in the same courtroom where Mr. Chun and Mr. Roh were two decades ago.

Mr. Moon’s election ended months of political turmoil and intrigue, set in motion when huge crowds began gathering in Seoul, the capital, last fall to demand Ms. Park’s resignation. The National Assembly voted in December to impeach her. The Constitutional Court endorsed the impeachment on March 10, formally removing her.

Her sprawling corruption scandal rekindled public furor over decades-old corrupt ties between government and corporations in South Korea, one of Asia’s most vibrant democracies.

Ms. Park and her longtime confidante, Choi Soon-sil, were accused of collecting or demanding bribes worth $52 million from three big businesses, including $38 million from Samsung. They were also accused of coercing scores of big businesses to make donations worth tens of millions of dollars to two foundations that Ms. Choi controlled.