Lai, the 74-year-old owner of the now-defunct Apple Daily newspaper, was found guilty of unlawful assembly charges alongside former journalist Gwyneth Ho Kwai-lam and former vice-chairperson of the now-dissolved Hong Kong Alliance Chow Hang-tung.

District Court judge Amanda Woodcock found Lai and Chow guilty of inciting others to take part in the 31st anniversary commemorative candlelight vigil, while Chow has been further convicted of taking part in an unauthorized assembly along with Ho.

Authorities charged more than two dozen pro-democracy politicians and activists over a vigil last year, which commemorated the victims of Beijing's Tiananmen crackdown in 1989.

The trio were the only ones to contest their charges in court, meaning they were the last to receive their verdict.

They argued they went to light candles in a personal capacity and had not "incited" others to join an outlawed rally.

But Woodcock dismissed those arguments as "frankly nonsensical".

"The reality was, any intention to come out and participate in the candlelight vigil in Victoria Park that night was an act of defiance and protest against the police," Woodcock ruled.

Lai, Chow and Ho are among dozens of activists already behind bars facing separate prosecutions under a strict national security law including charges of collusion with foreign forces, incitement to subversion, and conspiracy to commit subversion.

Previously, 16 politicians and activists - including prominent campaigner Joshua Wong Chi-fung - were sentenced to six to 10 months in jail over their roles in the vigil, with a few granted suspended sentences.