Six fugitives in Hong Kong have admitted trying to hinder criminal proceedings arising from their roles in the 2019 anti-government protests by boarding a Taiwan-bound speedboat in a thwarted escape bid two years ago.

The six men pleaded guilty before a deputy district judge at West Kowloon Court on Thursday to a joint count of doing an act or a series of acts tending or intended to pervert the course of public justice.

They were among 12 Hongkongers detained across the border in the summer of 2020 after their vessel was intercepted by Chinese coastguard in mainland waters. The fugitives were either facing prosecution or being pursued by police over offences linked to the 2019 unrest when they fled the city.

The fugitives’ vessel was intercepted by Chinese coastguard in mainland waters in 2020.

Explaining his preliminary observations before sentencing, Deputy District Judge Newman Wong Hing-wai said the present offence was more serious than a mere no-show in court.

Despite the lack of clear evidence showing any of the six was the mastermind behind the plan to abscond, the judge noted each of the defendants had actively taken part.

“The case of course involves a failure to surrender to custody, but there are other facets the court needs to consider, including the defendants’ admission the escape bid sought to obstruct criminal proceedings in Hong Kong,” Wong said. “This, I believe, can be seen as a challenge against Hong Kong’s judicial system.”

Prosecutors said the escape plan of the 12 had been detailed and organised, with the accomplices sharing responsibility for setting up safe houses, buying necessary supplies and funding their trip.

The group departed by speedboat from Po Toi O, in Sai Kung, under the guise of a fishing trip on the morning of August 23, 2020. They were arrested by mainland authorities the same day.

Ten of the 12 were jailed for seven months to three years after a closed-door trial at a Shenzhen court, whereas the remaining two were handed over to Hong Kong authorities without charge due to their young age.

The six who pleaded guilty on Thursday are Liu Tsz-man, 19, Cheng Tsz-ho, 20, Cheung Chun-fu, 25, Kok Tsz-lun, 21, and Cheung Ming-yu and Yim Man-him, both 23.

A seventh defendant, 32-year-old Li Tsz-yin, had indicated he would admit the charge, but was placed under quarantine by the prison service for being a close contact of a Covid-19 patient.

The deputy judge is expected to hear Li’s plea on Friday morning before passing sentence on all seven accused in the afternoon.

Fugitives Hoang Lam-phuc, 17, and Wong Wai-yin, 31, have previously been sanctioned for their roles in the trip. Three others, including national security law defendant Andy Li Yu-hin, 31, and two others who are still serving time across the border, have not been charged with a perversion offence.