The 77-year-old founder of the Apple Daily newspaper is charged with foreign collusion under Hong Kong's national security law, which Beijing imposed following huge and sometimes violent pro-democracy protests in 2019.

Lai has been kept behind bars since December 2020, reportedly in solitary confinement, with Western nations and rights groups calling for his release.

Aside from the collusion offence -- which could land him in prison for life -- Lai is also charged with "seditious publication" related to 161 op-eds he allegedly wrote.

The tycoon gave spirited courtroom testimony over more than 50 days during the trial, fielding questions about his political ideology, management style and overseas contacts.

Lai described himself at least twice as a "political prisoner", which drew sharp rebukes from the three-judge panel.

Hong Kong authorities have repeatedly rejected criticism related to Lai, saying last month that his case was "handled strictly on the basis of evidence and in accordance with the law".

Antoine Bernard of Reporters Without Borders said on Tuesday that Lai's treatment "exposes the authorities' ruthless determination to silence and suppress one of the most prominent advocates for press freedom amid Hong Kong's rapidly deteriorating media landscape".

- 'External political connections' -

Prosecutors showed the court a diagram titled "(Lai's) external political connections", arguing that he had exerted influence in the United States, Britain and Taiwan.

It featured headshots of top US political figures, including President Donald Trump, his former deputy Mike Pence and ex-secretary of state Mike Pompeo. Former Taiwan leader Tsai Ing-wen was also among those named.

Two prosecution witnesses, Chan Tsz-wah and Andy Li, also accused Lai of financially backing the advocacy group "Stand With Hong Kong" to run overseas newspaper ads supporting the 2019 protests.

Lai has denied calling for sanctions against China and Hong Kong and said he never advocated separatism.

Four other people who held senior roles in Apple Daily were called upon by prosecutors to testify about how Lai shaped the outlet's political stance.

The mogul said his newspaper championed democracy and freedom, adding that he had always disavowed violence.

"The core values of Apple Daily are actually the core values of the people of Hong Kong... (including) rule of law, freedom, pursuit of democracy, freedom of speech, freedom of religion, freedom of assembly," Lai said on the first day of his testimony.

Apple Daily was forced to close in 2021 after police raids and the arrests of its senior editors.

Lai is a British citizen and his son Sebastien reiterated in March calls for the Keir Starmer administration to do more, saying: "I don't want my father to die in jail."

Judges have indicated that a verdict could be reached by October.