Three anti-triad police officers were on Wednesday found guilty of colluding with gang members, after they acted to thwart a raid on an illegal gambling den in 2018.

The District Court heard that the gang was tipped-off that a police raid on an industrial building in Tsuen Wan was planned and that they should remove most of the gambling machines they had at the site.

Officers Chiu Kwong-lam, Lai Fuk-hong and Fu Yu-man told the gang to arrange for other people to be at the industrial building pretending to be gamblers, so police would have people to arrest during the raid.

But unbeknownst to Chiu, Lai and Fu, the "gang member" they gave this instruction to – during a meeting inside Tsuen Wan Police Station – was actually an undercover police officer.

In the end, the planned raid in June 2018 was called off.

Chiu, Lai and Fu were convicted of conspiracy to pervert the course of justice.

But in her ruling, deputy judge Katherine Lo said she couldn't be sure whether a fourth defendant, police officer Cheung Tsz-kin, was involved in the conversation with the undercover officer and therefore found him not guilty.

In mitigation, defence lawyers for Chiu, Lai and Fu urged the judge to consider how the convictions will affect their lives, saying the case didn't involve corruption or any self-interest.

Sentencing was adjourned to September 16.