His wife, a professor surnamed Chung, faces allegations that she forged a college presidential citation to help her daughter gain admission to medical school and about her family's dubious investment in a private equity fund (PEF).
The prosecution called her in a closed-door manner without her being exposed to the media, like in the previous two rounds of summoning.
Chung was indicted for alleged forgery in early September.
|Justice Minister Cho Kuk (Yonhap)|
State prosecutors first questioned her Thursday, but the probe ended earlier than expected as she cited health problems.
During the probe on Saturday, she spent most of the time reviewing whether investigators properly wrote a report on her first questioning.
The prosecution reportedly plans to concentrate on allegations that she may have conspired with Cho's nephew for suspected involvement in the PEF operation.
Chung and her two children invested more than 1 billion won ($837,380) in the fund, months after Cho was named as senior presidential secretary for civil affairs in May 2017.
Cho denied playing a role in the investment during his confirmation hearing.
Meanwhile, a younger brother of Cho will face a court hearing later in the day over corruption allegations in connection with a private school foundation that Cho's mother is running.
On Monday, he requested a delay in the hearing on whether to detain him, citing health problems.
But the prosecution executed a warrant to bring him to the court on the judgment that his health has no problems. (Yonhap)