The sister of gangland boss Willem Holleeder has told a courtroom that locking him away for life is the ‘only medicine’ for his criminal tendencies.

Spectators queued outside the high security ‘Bunker’ courthouse in Amsterdam’s Osdorp district on Monday for the first day of testimony by Astrid Holleeder, whose evidence forms the bulk of the case against her brother.

Willem Holleeder, 59, is standing trial for involvement in six murders, including Cor van Hout, a fellow member of the gang that kidnapped beer magnate Freddy Heineken in 1983.

Astrid Holleeder has published two books in recent years on her role as her brother’s confidante. She said she eventually went to police to protect herself and her sister Sonja from Willem’s threats: ‘The amount of attention he paid to Sonja and the children was extreme. He doesn’t learn from previous punishments. That put us in danger.’

She was audibly moved as she told the court: ‘I don’t want revenge, I have no hard feelings. He’s sick and the only medicine is to lock him up… A dog who bites children has to be put down. It’s demented.’

Heineken kidnapping

Astrid said she had worked for her brother as a teenager when he ran a casino in Amsterdam’s red light district, which was bought with the proceeds from the Heineken kidnapping. The ransom money was worth €16 million at today’s values.

‘My moral awareness came later,’ she said, but by that time she was entangled in her brother’s criminal empire. Astrid said Willem was a dominant personality who only contacted people when he needed them. ‘I couldn’t allow myself not to go to him when he wanted, he would have just looked for me everywhere.’

Willem Holleeder looked on largely impassively in the courtroom, occasionally taking notes or sitting with his arms folded, as his youngest sister described how she cultivated his trust by developing a strategy of not contradicting him.

‘You don’t tell Pablo Escobar, “What a bastard you are”; you say: “Your hair looks nice”. That’s how it was for us too.’

Ultimate betrayal

Astrid wept as she described the decision to take her evidence to the police as ‘the ultimate form of betrayal’, adding that she still loved her brother and sympathised with him. ‘Throughout my life I have done nothing more than love people I didn’t like,’ she said.

Willem Holleeder’s lawyers will question his sister in court on Friday. Holleeder is accused of ordering five murders and one manslaughter between 2002 and 2006. The public prosecution service has said it wants to destroy his public image as a ‘cuddly criminal’ and chat-show guest and show him to be ‘a common criminal, a blackmailer and, in our opinion, a cold killer.’