The national security trial of dozens of people — from former pro-democracy legislators to activists and legal scholars — has begun in Hong Kong more than two years after they were arrested in pre-dawn police raids across the territory.

The defendants are accused of “subversion” for organising an unofficial primary to choose their candidates for the 2020 Legislative Council election that the government later postponed blaming the coronavirus pandemic.

There was a heavy police presence, including officers with dogs, outside the West Kowloon Magistrates’ Courts building ahead of the proceedings.

Some people began lining up overnight for a seat in the public gallery, with the queue snaking around the building by the morning.

“There’s certainly huge sympathy for the people who are standing trial,” said Al Jazeera’s Richard Kimber, reporting from Hong Kong. “There’s certainly a lot of frustration that it’s taken this long to get to this stage and that those who’ve been detained have not been able to speak out since they were arrested.”

Those charged include prominent activists Leung Kwok-hung, known as “Long Hair”, and Gordon Ng Ching-hang, who faces potential life imprisonment as one of five people accused of being a “major organiser” of the primary.

“There’s no crime to answer. It is not a crime to act against a totalitarian regime,” defendant and former legislator Leung told the court.

Judge Andrew Chan responded that the hearing was a “solemn occasion” and asked for respect from the defendants and members of the public.

Those who have pleaded guilty include internationally-known activists like Joshua Wong, Claudia Mo, a former journalist turned legislator, and law expert and former academic Benny Tai.

Together, the 47 accused account for much of what remains of Hong Kong’s pro-democracy leadership after mass protests calling for political reform in 2019 came to an inconclusive end with the COVID-19 pandemic, and the national security law pushed many into exile.

Prosecutors have described the primary — held so the democrats could put forward their strongest candidates for the Hong Kong Legislative Council(Legco) election — as a “vicious plot” to subvert the government and wreak “mutual destruction” on it by taking control of the city’s legislature.

“Running for the Legco election is what kind of illegal means, what kind of violent threat?” Chan Po-ying, chairwoman of the League of Social Democrats and Leung’s wife, said outside the court.

The trial is expected to continue for 90 days.

Sentencing of all the defendants will take place after it has concluded.

Under the security law, which took effect on June 30, 2020, the defendants face up to three years in prison for conspiracy to commit subversive activities, between three and 10 years imprisonment for “active participation” in the conspiracy, and between 10 years and life imprisonment if they are deemed “principal offenders”.

Hong Kong was returned to China in 1997 under a “one country, two systems” formula meant to guarantee its freedoms and an independent legal system for at least 50 years.

Beijing imposed the broadly-worded security law on the city after months of protests that began as mass marches against plans to allow extradition to the mainland, and evolved into a campaign for democracy that sometimes turned violent.

As well as subversion, the law punishes actions deemed “secession”, “collusion with foreign forces”, and “terrorism” with up to life in prison.

A year after it was imposed, rights group Amnesty International said it had “decimated” freedoms in Hong Kong and put the territory on the road to becoming a police state. (Al Jazeera)

•There was heavy police presence outside the West Kowloon Magistrates' Courts building ahead of the opening of the trial of the 47 pro-democracy activists [Tyrone Siu/Reuters]

Update news