Taipei, Taiwan – A Hong Kong court has sentenced a leading pro-democracy advocate to 10 years in prison and handed dozens of other activists years-long jail terms in the Chinese territory’s largest national security case.

Benny Tai, a 60-year-old legal scholar who played a prominent role in Hong Kong’s pro-democracy protests in 2014 and 2019, was handed the lengthy sentence on Tuesday after prosecutors cast him as the “organiser” of a conspiracy by activists and politicians dating back to July 2020.

Tai and 44 others either pleaded guilty or were found guilty of offences related to organising an unofficial primary election to choose pro-democracy candidates for the city’s legislature.

The activists sought to elect lawmakers who would vote down the city’s budget to force the dissolution of the legislature and then the ouster of the city’s leader – something that is allowed for under Hong Kong’s Basic Law.

Prosecutors alleged that the group plotted to “overthrow” the government.

After Tai, the lengthiest sentence was handed down to Owen Chow, 27, who received seven years and nine months for running as a candidate in the election.

Former journalist Gwyneth Ho, 34, received seven years.

Both pleaded not guilty during the trial.

Australian citizen Gordon Ng, who urged Hong Kongers to vote in the primary on social media and in the media, was sentenced to seven years and three months.

Many of the group had been on remand for years after being denied bail during a marathon hearing in March 2021.

Out of 47 defendants arrested by Hong Kong’s national security police in a predawn raid in January 2021, 31 pleaded guilty, including Tai.

In May, the court found 14 of the remaining activists guilty of subversion and acquitted two others, former district councillors Lawrence Lau and Lee Yue-shun.

The trial, which ran for 118 days after its start was repeatedly delayed, was overseen by three hand-picked judges and eschewed many conventions of Hong Kong’s common law legal system, including trial by jury and the presumption in favour of bail.

Defendants who pleaded guilty received shorter sentences in mitigation.

Among them were former journalist and legislator Claudia Mo, 67, who received four years and two months, and internationally well-known activist Joshua Wong, 27, who received four years and eight months.

Observers said they expect prosecutors to file appeals seeking longer sentences for at least some of the activists, with Tai and Wong among the likely candidates.

Under Hong Kong’s Beijing-drafted national security law, defendants charged as “primary offenders” face a maximum punishment of life imprisonment, while lower-level offenders face sentences of between three and 10 years.

As the sentences rolled in on Tuesday, it was an emotional moment for Kevin Yam, a former Hong Kong lawyer who is now based in Australia.

During his career in Hong Kong, Yam, who is wanted by city authorities for alleged national security offences, knew or engaged with many of the 45 defendants, including Tai.

“I’ve known [Tai] for over 20 years, and the thought of him going in for 10 years is heavy,” Yam told Al Jazeera.

“One day is too heavy. I mean, what has he done? He’s organised an informal vote on something. Basically, all 45 of the people convicted are being punished for seeking to work within the constitutional process.”

The sentences also drew swift criticism from foreign governments and rights groups.

“Running in an election and trying to win it is now a crime that can lead to a decade in prison in Hong Kong,” said Maya Wang, associate China director at Human Rights Watch.

“Today’s harsh sentences against dozens of prominent democracy activists reflect just how fast Hong Kong’s civil liberties and judicial independence have nosedived in the past four years since the Chinese government imposed the draconian National Security Law on the city.”

Australian Foreign Minister Penny Wong told the media on Tuesday that Canberra had lodged a complaint with the Hong Kong and Chinese authorities over the sentencing of Ng.

“Australia has expressed our strong objections to the Chinese and Hong Kong authorities on the continuing broad application of national security legislation, including in application to Australian citizens,” Wong said.

The United States consulate in the city said it “strongly condemns” the sentences.

Hong Kong was roiled by at times violent antigovernment protests in 2019 after then-leader Carrie Lam proposed legal changes to allow criminal suspects to be extradited to mainland China.

The protests quickly escalated into the largest antigovernment movement on Chinese soil since 1989’s Tiananmen Square protests as Hong Kong residents demanded greater political freedoms, including direct elections to choose the city’s leader.

In 2020, Beijing imposed sweeping national security legislation on the city, criminalising secession, terrorism, subversion, and collusion with foreign forces.

Earlier this year, Hong Kong passed local national security legislation based on “Article 23” of the city’s mini-constitution, introducing a range of new offences including theft of state secrets and treason.

Between July 2020 and December 31, 2023, 286 individuals were arrested by national security police under the city’s national security or colonial-era sedition laws, according to a tally by the Georgetown Center for Asia Law.

Of those, 156 people have been charged, including the so-called Hong Kong 47.