Tong Ying-kit, who hit officers while riding a motorcycle with a protest flag, is accused of terrorism and inciting secession. He could be sentenced to life in prison.

HONG KONG — Nearly a year ago, a 23-year-old ramen cook rode a motorcycle through a Hong Kong neighborhood, flying a large flag emblazoned with a popular anti-government protest slogan. He collided into several riot police officers as they tried to stop him.

In a different era, the rider, Tong Ying-kit, might have been accused of dangerous driving and assaulting a police officer. Instead, the authorities arrested him last July under a draconian national security law Beijing had imposed on Hong Kong, only hours earlier, that took aim at dissent and other political activity challenging China’s rule.

Mr. Tong stood trial on Wednesday, the first among the more than 100 people in Hong Kong who have been arrested under the sweeping new rules. His case is a test of how the city’s vaunted judicial system, based on British common law principles of fairness and independence, will interpret and enforce Beijing’s far-reaching security law, in which political crimes are vaguely defined. China says the law is necessary to root out threats to Beijing’s sovereignty, but human rights activists, opposition leaders and scholars have said the law puts the city’s judicial independence in peril.

“The national security law constitutes one of the greatest threats to human rights and the rule of law in Hong Kong since the 1997 handover,” wrote Lydia Wong and Thomas Kellogg, scholars at Georgetown Law School, in a report in February.

The authorities have accused Mr. Tong of terrorism, for crashing his motorcycle into the police officers, and incitement to commit secession, for displaying a protest slogan the authorities say is a call for independence for the semiautonomous Chinese territory. If convicted, he could be sentenced to life in prison.

Mr. Tong’s fate could indicate how the courts will handle the dozens of other national security cases in the coming months. The court’s ruling on the popular protest slogan on Mr. Tong’s flag, in particular, will be a clear sign of how far the law goes in criminalizing political speech.

Mr. Tong in a police van last year. He is the first person charged under the new national security law to stand trial in Hong Kong.
Vincent Yu/Associated Press

The policing of speech has gained prominence in recent months as the authorities have enforced the security law against opposition politicians and the media. It marks a dramatic change in a city where residents have long cherished the freedom to air their political views, no matter how critical they may be of the government.

“In the new Hong Kong, your opinion, your wrong opinion, if articulated, can be evidence of subversion, which is quite close to how the situation is in China,” said Steve Tsang, director of the SOAS China Institute in London.

The message to the people of Hong Kong is “watch what you say, because what you say may be used against you,” he said. “It’s really, really quite terrifying.”

Citing purported violations of the law, the authorities have arrested more than 50 opposition politicians — most of the leading figures in the city’s beleaguered pro-democracy camp — for organizing an informal election primary, accusing them of trying to overthrow the government.

They have arrested Jimmy Lai, a pugnacious media tycoon, and top editors at his stridently pro-democracy newspaper, Apple Daily, accusing them of conspiring to collude with foreign forces, the first time the law has been used to target news organizations. On Wednesday, the police also arrested an editorial writer at the newspaper, as part of the same investigation.

The authorities have also used the security law, to a lesser extent, against ordinary protesters such as Mr. Tong. Little is known about Mr. Tong, even now, one year after his arrest. A former lawmaker who has met him said he was a cook at a ramen restaurant who took part in pro-democracy protests in 2019 and helped provide first aid.

Even before Mr. Tong’s first day in court, his case has raised questions about whether the security law has empowered the authorities to chip away at the legal protections that had until now been typically granted to defendants.

One significant change under the new law is that defendants like Mr. Tong have been denied bail and held in police custody for months. The law requires defendants to convince judges that they will not endanger national security, a vague standard that is hard to meet. Only around a dozen out of the more than 50 people charged under the law have been released on bail.

Jerome Favre/EPA, via Shutterstock

Mr. Tong is also being denied a trial by jury, which has been standard practice when defendants face serious punishments. Teresa Cheng, Hong Kong’s justice secretary, ordered a bench trial for Mr. Tong, citing a clause in the security law that allows her to do so if she thinks jurors’ safety is at risk. The three judges hearing his case are among a group chosen by Hong Kong’s chief executive, whose power to do so under the new law has been seen by critics as eroding the autonomy of the courts.

How the judges parse the specific charges against Mr. Tong will be scrutinized for whether the law is being used to curb genuine threats to China’s security, or merely to stifle voices critical of the ruling Communist Party.

Mr. Kellogg of Georgetown questioned whether Mr. Tong’s act of driving into the police officers qualified as terrorism. “It’s not clear to me that Tong was engaged in the sort of organized, planned and often large-scale political violence that is the hallmark of terror attacks,” he said.

The police obtained more than 800 videos of Mr. Tong’s ride, and about 200 of those are expected to be introduced into evidence during his trial. The prosecutors and defense attorneys are likely to argue over whether Mr. Tong intentionally drove into the police officers. Three officers were injured as they moved to stop him.

The terrorism charge, and the allegation of violence it carries, makes Mr. Tong’s case unusual. But his other offense, centering on political expression, has become commonplace.

The slogan emblazoned on his flag, “Liberate Hong Kong, Revolution of Our Times,” was coined by a now-imprisoned activist, Edward Leung, in 2016. During the 2019 protests it became ubiquitous: a rallying cry that was chanted by students in schoolyards and protesters in street marches, emblazoned on banners and graffitied on walls that have since been painted over.

Lam Yik Fei for The New York Times

Mr. Tong’s lawyers are expected to argue, as have many protesters, that the phrase represents a desire to reclaim Hong Kong’s unique identity from the heavy-handed influence of Beijing. The government has said the slogan represents a call for independence, and thus violates the security law.

That a political slogan could constitute a criminal offense is still a new and unsettling idea in Hong Kong, where residents had for decades enjoyed the right to protest, freedoms largely unseen in mainland China.

“We must bear in mind the context. The words he had, we need to understand that during that period those words were quite commonly spoken and exhibited on many flags and banners in peaceful and even non-peaceful protests in Hong Kong,” said Eric Cheung, a law lecturer at the University of Hong Kong.

“The meaning of these words differ from person to person,” Mr. Cheung said. “You now say that using these words carry only that meaning which amount to intention to subvert the country, I think that is a debate.”

Even if Mr. Tong is not convicted of terrorism, he faces a separate charge of causing grievous bodily harm by dangerous driving, which carries a maximum penalty of seven years in prison.

As he awaited trial, Mr. Tong was sharing a cell with 10 men, according to Shiu Ka-chun, a former lawmaker who wrote on his social media page last year that he had been visiting him regularly. Mr. Shiu declined to comment about Mr. Tong. But in his social media posts, he wrote that Mr. Tong has been reading books on history, including a memoir by Lee Teng-hui, Taiwan’s first democratically elected president.

“For those comrades who are continuing to take a stand, he says wait and be patient,” Mr. Shiu wrote. “For those who have left Hong Kong, he looks upon that calmly and thinks, ‘Hong Kong is in your hearts, everywhere is Hong Kong.’”