Hong Kong's High Court started on Monday to hear the mitigation plea of Jimmy Lai Chee-ying, the final step before sentencing in a landmark national security trial that could see Lai jailed for life.

Lai, 78, was last month found guilty of two counts of conspiracy to collude with foreign forces under the national security law, and conspiracy to publish seditious material. Lai has denied all charges.

The judges wrote that Lai had used his influence and the Apple Daily tabloid "to carry out a consistent campaign with a view to undermine the legitimacy or authority" of China and Hong Kong.

They added that Lai's evidence was at times "contradictory, inconsistent, evasive and unreliable". Eight other defendants have pleaded guilty. Five of them have become prosecution witnesses, including Cheung Kim-hung, former CEO of Lai's once-listed company, Next Digital; Apple Daily's former associate publisher Chan Pui-man; and former editorial writer Yeung Ching-kee.

The mitigation hearings for all the defendants start at 10am and are expected to last four days. Sentencing will take place at a later date.

Dozens of people have been queuing outside the court building since Friday, hoping to see Lai and other defendants. They have stayed overnight and slept on the street with blankets and cardboard.