National security police chief superintendent Steve Li on Monday said the force welcomed the sentences of former media tycoon Jimmy Lai and his eight co-defendants over conspiracies to collude with foreign forces and printing seditious materials.

Lai was sentenced to 20 years behind bars — the toughest penalty to date over National Security Law convictions, while the eight others were given jail terms of between six years and three months and 10 years.

Li said the sentences demonstrated that the court confirmed the seriousness of the crimes, and that Lai was the mastermind of the conspiracies.

The chief superintendent said the court proceedings were the best example of Hong Kong's rule of law.

"The entire process, spanning five and a half years, fully demonstrated the vigour and transparency of the administration of justice," Li told reporters at a briefing outside the West Kowloon Court building.

"In 156 days of open court hearings, these exhaustive procedures demonstrated that the court applied the strictest criminal standards of proof and open proceedings, representing the finest embodiment of the rule of law in Hong Kong."

Li said he personally found the sentences to be appropriate in reflecting the facts of the case.

However, he said police would discuss with the Department of Justice to see whether there was a need to lodge an appeal over the length of the sentences.

Li noted that five defendants who became accomplice prosecution witnesses received lighter sentences.

He said this reflected a clause under the security law that provides for the possibility of more lenient punishment for those who expose the criminal conducts of others.

The chief superintendent went on to say that Hong Kong's system allows for criminals to be sent to other countries to serve their sentences, but this was a legal matter for the two jurisdictions to handle.