A South Korean court has sentenced former president Yoon Suk Yeol to five years in prison for mobilising presidential security forces to block his own arrest and abusing his powers. It is the first judicial ruling linked to the events surrounding his failed martial law declaration in December 2024.

The ruling is separate from Yoon’s main insurrection trial, where prosecutors earlier this week sought the death penalty and a verdict is due next month.

Seoul central district court found Yoon guilty of special obstruction of official duties, abuse of power and falsifying documents, saying he had “disregarded the constitution” and shown no remorse. His legal team has said he will appeal against the ruling.

The presiding judge, Baek Dae-hyun, said Yoon “deserves condemnation” for his actions.

Yoon stunned South Korea late on 3 December 2024 when he declared martial law, dispatching police and armed troops to the national assembly. Lawmakers rushed to override the decree, with some climbing over fences to reach the chamber before voting to lift the order.

The emergency rule lasted six hours before Yoon backed down. In the separate insurrection case, prosecutors allege he attempted to use military force to paralyse the legislature, arrest political opponents and seize control of the national election commission.

Weeks after martial law collapsed, investigators from the country’s corruption investigation office attempted to arrest Yoon on insurrection-related charges.

Supporters of Yoon Suk Yeol hold placards and flags as they rally outside the Seoul central district court in Seoul on Friday. Photograph: Jeon Heon-Kyun/EPA

He refused to comply, barricading himself inside his residence and deploying hundreds of presidential security service officers to block a court-issued arrest warrant by sealing the compound with vehicle barricades and human chains.

“The defendant abused his tremendous influence as president to obstruct lawful warrant execution, effectively privatising security officials sworn to serve the Republic of Korea into his personal troops,” Baek said in a televised ruling. “His crimes are extremely serious in nature.”

The court also criticised Yoon’s conduct in the run-up to the martial law declaration. He selectively summoned only loyal cabinet members to a late-night meeting, excluding nine others in order to rubber-stamp the decision without meaningful deliberation.

He later signed backdated documents to create the false appearance of proper cabinet approval.

“Emergency martial law should only be declared in the most exceptional circumstances when no other means exist to resolve a national crisis,” Baek said. “The constitution specifically requires state council deliberation precisely to prevent presidential abuse of power and arbitrary action.”

Friday’s conviction marks the opening act in a reckoning without parallel in South Korea’s democratic history. Yoon faces seven additional criminal trials, including the insurrection case, where prosecutors are seeking either the death penalty or life imprisonment.

Other cases, some brought by separate special prosecutors, include allegations that he ordered drone incursions into North Korean airspace to provoke a response that could be used as a pretext for martial law.

The insurrection verdict is scheduled for 20 February. That case centres on allegations that Yoon, former defence minister Kim Yong-hyun and former police commissioner Cho Ji-ho orchestrated the deployment of armed troops to the national assembly.

Yoon’s wife, Kim Keon Hee, faces a separate verdict on 28 January on stock manipulation and bribery charges, carrying a prosecutorial demand of 15 years’ imprisonment and a 2bn won (£1m) fine.

Former prime minister Han Duck-soo is due to receive a verdict on 21 January on charges of aiding insurrection.