What is said to be the Netherlands’ biggest and longest-running trial came a step nearer to completion on Thursday with four men being sentenced to life imprisonment for their role in a string of gangland killings.

Three of the men – Jesse R, Mohamed ’Moppie R and Siegfried S – were jailed for life at their earlier trial but the fourth, Dino Soerel, had been found not guilty because of a lack of evidence.

Two crown witnesses – Peter la Serpe and Fred Ros –  were sentenced to eight and 14 years respectively. Their evidence was considered crucial in securing the murder conviction against Soerel. Ros, who had already served two-thirds of his sentence, will not go back to jail.

The evidence from the crown witnesses led to the re-arrest of gangland leader Willem Holleeder at the end of 2014. He is being investigated for his role in a number of other killings.

Three other men were also jailed on Thursday for up to 13.5 years for their roles in the killings.

Property magnate

The case centred on gang-related killings between 1993 and 2006, including the murders of property magnate Kees Houtman in 2005 and cafe owner Thomas van der Bijl one year later. The defendants were also charged with planning other killings, membership of a criminal organisation, money laundering and the illegal possession of weapons.

By the time the original trial actually started in 2009, some 257 witnesses had been heard during the police investigation, 500 telephones were tapped and the paperwork filled 250 files.

The defence still have the option of appealing to the Supreme Court.