This trial marked the first time a former First Lady had to appear in court, after her husband was executed for a plot to establish martial law.
Kim Keon Hee was arrested in August on a series of charges, including securities manipulation and corruption. She appeared directly at the Seoul Central District Court, being escorted by security personnel.
In a dark vest with tight hair, the former First Lady wore a card with the number of Prisoner 4398 on her chest.
The trial began with a confirmation of the defendant's identity and profession, then she briefly replied: "I am unemployed". She also stated her date of birth and refused to request a trial with a jury.
The incident means that South Korea currently has both a former president and a former first lady facing criminal proceedings at the same time.
Ms. Kim Keon Hee has long been investigated with many suspicions related to her role in stock manipulation.
Public opinion has been exploding with outrage since 2022 when a left-wing monk filmed a video giving her a Dior bag, and she seemed to have received it.
She was also accused of interfering in Mr. Yoon's party's nomination process, violating election laws.
Legal experts say the trial could see the former president and his first lady summoned at the same time for alleged interference in parliamentary elections.
During his presidency, Mr. Yoon violated three special investigation bills passed by the parliament - under the control of the opposition - to investigate allegations against Ms. Kim, with the most recent denial taking place at the end of November 2024.
