SEOUL, South Korea — An South Korean appeals court has reduced the prison sentence of a former prime minister convicted of rebellion for his role in then President Yoon Suk Yeol’s ill-fated imposition of martial law in December 2024.

Ex-Prime Minister Han Duck-soo, a Yoon appointee, was sentenced to 23 years by a Seoul court in January. Yoon was sentenced to life in prison for rebellion the next month.

On Thursday, the Seoul High Court upheld most of Han’s convictions, but reduced his sentence to 15 years.

It upheld charges including that Han tried to create the appearance of legitimacy for Yoon’s illegal decree by getting it endorsed at a Cabinet meeting and discussing plans to cut off of water and electricity to critical media agencies. The court also affirmed convictions for falsifying the martial law proclamation, for destroying it and for lying under oath.

The Seoul High Court said that Han’s “criminal liabilities are very grave” because he “abandoned his immense responsibilities” as the No.2 official in the Yoon administration and participated in the rebellion.

Park SungBae, a lawyer who specializes in criminal law, said that both the district and appeals courts viewed Han’s charges as very grave. Park said that the Seoul High Court still likely determined that a 15-year term is appropriate for Han, given rulings on others involved in Yoon’s martial law such as his Interior Minister Lee Sang-min who got seven years in prison.

The special prosecutor requested a 15-year sentence for Han during his trial at the Seoul Central District Court. Park said that the 23 years the court handed down was higher than expected but still within the normal range for Han’s crimes.

Han and the prosecutor have seven days to appeal Thursday’s ruling to the Supreme Court, the country’s top court.

Han, 76, is a career bureaucrat who served as prime minister twice during his 40 years of public service, first under liberal President Roh Moo-hyun from 2007 to 2008 and later under the conservative Yoon. Han was one of three people who served as caretaker leaders after Yoon was suspended from office over his martial law gambit.

Yoon was eventually impeached by lawmakers before the Constitutional Court permanently removed him from office in April last year. His liberal rival Lee Jae Myung succeeded him after winning a snap election.