Cardinal Joseph Zen, 90, one of the most senior Catholic clerics in Asia, and five others were accused on Monday by government prosecutors of using a now-disbanded charity fund for pro-democracy protesters as a front for "political activities".
The six, including Cardinal Zen, barrister Margaret Ng, scholar Hui Po Keung, politician Cyd Ho, and singer Denise Ho, were trustees of the "612 Humanitarian Relief Fund" that helped protesters arrested during pro-democracy, anti-China protests in 2019 pay their legal and medical fees.
They were arrested under national security laws in May for allegedly asking for foreign sanctions, but were later charged with a lesser offence of failing to register their fund as a society under local laws.
The maximum penalty if convicted is a fine of up to HK$10,000 (£1,181). All have pleaded not guilty.
At the opening of the trial, prosecutor Anthony Chau said the fund had been used for "political activities", including sponsoring surveys and activities related to mass protests.
"The goal of the fund was to raise the political demands of the anti-extradition bill protests to the international level," Chau told the court.
Prosecutors added that the fund raised around HK$270 million (£31.2 million) from 103,000 public donations, and was partly used to sponsor political, non-charity events and overseas lobbying, including persuading the European Union to provide asylum to Hong Kongers and to sanction Chinese and Hong Kong officials.
In a video played in court, Cardinal Zen was shown saying: "We hope every citizen can be encouraged by this fund."
Principal Magistrate Ada Yim said it was not for the court to decide whether the political goals or demands were right or wrong.
"Why must we equate politics to bad things? It can be a neutral thing," Yim said.
The silver-haired Zen who appeared in court with a walking stick, has long been a staunch advocate of democratic rights and freedoms and a critic of the Chinese Communist Party.
While his arrest was condemned by some Western governments, the Vatican was criticised for its relative silence at a time when it was seeking to extend an agreement on the appointment of bishops in China, that includes accepting those previously appointed by the Chinese government.