“The defendant was not a lone protester quietly carrying a flag bearing the slogan amongst a sea of protesters,” read the judgment delivered at the Court of First Instance. “He deliberately challenged a number of police check lines in order to attract as much attention to the secessionist message on the flag as possible and to leave a great impact and a strong impression on people.”

How many meanings are there in protest slogan ‘Liberate Hong Kong’?

But the bench accepted the incitement offence was not the worst of its kind, as Tong had acted alone and lacked an elaborate plan to separate Hong Kong from the rest of the nation.

They found he had committed a terrorist act causing grave harm to society by running into the three police officers – a symbol of law and order – and intimidating members of the public, especially those with opposing political views, by that action.

In weighing that offence, the judges said Tong had turned his motorbike into a lethal weapon used against the officers.

“What the defendant did was calculated and deliberate acts which created a very dangerous situation for the road users and which indeed caused injuries to three police officers,” the judgment read.

But they agreed the injuries suffered by the officers were not “serious” as alleged by the prosecution and the starting point for sentencing for the charge should be between three and 10 years in jail. Under the security law, terrorism carries a maximum penalty of life imprisonment.

Tong, who has already spent nearly 13 months in custody, is expected to serve his sentence at the high-security Stanley Prison and will not be eligible for early release for at least five years.

Tong’s counsel Clive Grossman SC said his client would lodge an appeal.

Madam Justice Esther Toh Lye-ping said the two terms should in principle be served separately as they concerned different crimes, but the bench had decided to order partially concurrent sentences.

“We consider that this overall term should sufficiently reflect the defendant’s culpability in the two offences and the abhorrence of society, at the same time, achieving the deterrent effect required,” she said.

‘Liberate Hong Kong’ slogan ‘very risky’, scholars, experts warn after ruling

At Thursday’s mitigation hearing, the defence counsel described the accused as “a decent young man” who had committed the offences out of stupidity and was genuinely remorseful. Tong had been living with his father and younger sister at a public housing estate following his parents’ divorce.

The court heard the defendant had taken first aid courses and attended protests two years ago – not to cause a disturbance, but to offer medical attention to those injured in the unrest.

But Toh said those considerations were outweighed by the serious nature of the offences.

The court also found it “obvious” that Tong should be disqualified from driving for a decade, given he was only holding a probationary licence at the time of the crime, his previous traffic convictions and the “very dangerous” manner in which he steered the motorbike into the officers.

The judges also found little merit in referring to previous sentences meted out for terrorism in other common law jurisdictions, such as Britain, Australia and Canada, saying: “The cultural and socio-economic situation pertaining at the material time when a sentence is considered by the court would not be identical”.

Secretary for Security Chris Tang Ping-keung said he welcomed the conviction and his bureau would study the appropriateness of the sentence before deciding whether to take any further steps.

The court has ruled that the slogan could constitute a meaning for Hong Kong independence,” he said. “We believe a Hongkonger who is a law-abiding citizen, who does not want to endanger national security or separate the country, would not be telling such a slogan.”

Letters submitted to the court described Tong as simple-minded and kind-hearted, as well as a filial son who supported his family and his younger sister’s studies abroad.

Tong’s father believed his son was influenced by “bad publications that led to his wrong act”, while his aunt took the view that her nephew had been “affected by some people in the society and the media’s false reporting”.

His maternal grandmother, who is battling cancer, wrote to the court asking for “one more hug” from her grandson before she died.

Tong also told the court in his own letter he had now come to realise that political views were matters of perspectives and should not be more important than human decency. Society should put aside hatred, he added.

Legal experts have since warned against the use of the slogan in future, while at least one mainland Chinese think tank has suggested other popular chants that challenge the local and central governments, such as “Five demands, not one less”, could also be deemed problematic.

Liberal academics have called the ruling another blow to freedom of expression.

Thomas Kellogg, executive director of the Georgetown Centre for Asian Law, said the “harsh” sentence imposed on Tong had dashed hopes that the court would take into account the awareness of the security legislation and administer a lighter sentence on early defendants.

“People can only shape their behaviour after the initial lines of what the national security law covers have been drawn,” he said, adding that it did not bode well for 47 opposition activists who were earlier charged with subversion for their part in an unofficial opposition primary election last year.

He also said it was unfortunate that judges had ruled that the acts to incite secession were of a “serious nature”. “If Tong’s act of carrying the banner is serious, what acts ... are not serious? I worry that the court has essentially expanded the serious nature provision to cover almost all acts of inciting secession,” he said.

Britain-based opposition activist Nathan Law Kwun-chung called the sentence “outrageous”, raising concern over free speech. “The sentencing guideline is unclear, and it gives the judge the power to determine whether a slogan can be seen as ‘capable of’ inciting secession. This is an extremely low threshold to lock an individual in jail for years,” he said.