Hong Kong’s High Court has convicted pro-democracy activist and newspaper founder Jimmy Lai on three charges under the 2020 National Security Law, including conspiring with foreign forces to threaten China’s national security and publishing seditious material.

Lai, 78, who has been in detention since December 2020, now faces the possibility of a life sentence.

Judges described him as the “mastermind” of a criminal conspiracy, citing his alleged attempts to involve the U.S. against China, while Lai had pleaded not guilty and testified for 52 days.

Human rights and press freedom groups condemned the verdict, calling it a severe blow to media freedom in Hong Kong and a form of political persecution, Al-Jazeera has reported.

Lai is scheduled for a pre-sentencing hearing on January 12, and it remains unclear whether he will appeal the verdict.