A man previously acquitted of the murder of a man in Wellington in the 90s has been jailed for nine years for his part in a European drug ring that built sound-proof torture chambers.

William Jan H. Haanstra, 44, was one of 10 people sentenced in Amsterdam last week, two years after Dutch police discovered seven shipping containers customised into prison cells – and a torture chamber.

Dutch authorities say the shipping containers were planned with precision – six were soundproofed cells, and one was kitted out as a torture chamber.

In this screenshot taken from video made available by the Netherlands Police on Tuesday, July 7, 2020, a view of a sea container equipped as a torture chamber. Photo / Dutch police

The Guardian reports the torture chamber had a dentist's chair with restraints, saws, pliers, secateurs and scalpels – as well as equipment needed for waterboarding people and a large freezer.

Dutch police say it's likely the members of rival drug gangs would be kidnapped and held in these rooms.

The plan involved multiple teams of people, fake police uniforms, traffic stops and bulletproof vests – a plan uncovered when police cracked an encrypted messaging system.

Those arrested claimed they never planned to actually torture people and the cells were built purely as a way to frighten their rivals.

The sentences range in severity from one to nine years and an eleventh person was acquitted.

It's not Haanstra's first experience with the law. In 1999 he was accused of killing drug dealer Terri King execution-style in the Tararua Ranges.

King had been importing drugs from South Africa – and the Crown alleged Haanstra owed him $8000.

The Crown claims Haanstra lead King into the ranges with a lure of a buried cache of MDMA, then shot him in the back of the head with a rifle.

A hunter discovered King's body two months later.

Haanstra was the last known contact of King, but the then 22-year-old denied any involvement in the death.

His defence said King's death was likely due to relationships souring between King and the South African men he was importing drugs from.

After a two-month, high-profile trial, Haanstra was acquitted. King's murderer was never found.