"Dutroux was allowed back into society like a grenade with the pin removed, waiting to explode at any moment," wrote Marc Metdepenningen, a journalist who has covered the case extensively.
Worse still, police searched the house where Julie and Melissa were hidden but failed to find them. Once they heard cries for help but accepted Dutroux's claim that the noise was coming from children in the street. No listening devices, heat sensors or other equipment was used, but police found handcuffs, chloroform, vaginal cream and a gynecological mirror.
Potential connecting information fell through the cracks between different police services, and particularly between units in the Dutch-speaking Flanders and Francophone Wallonia.
Grief and fury over the killings erupted into protests known as the Marche Blanche in 1996, when 350,000 people took to the streets of Brussels.
That was not the end of the story. Two years later the most hated man in the land escaped briefly; and it emerged recently that he had been allowed to correspond with a 15-year old girl for two years.
Dutroux mounted a bid for release on the grounds that he had been held for too long without trial and in inhumane conditions.
Psychologists describe him as a having a strong sense of his own victimhood.
There is anger from the victims' parents about how they have been treated.
"It took four corpses, including my child's, before they would listen to us," said Gino Russo, Melissa's father.
"To be in court would sully the memory of my daughter," said Jean-Denis Lejeune.
For them and many others, the crucial question is whether Dutroux is telling the truth in hinting that he procured girls for a network of establishment figures, and that a massive cover-up is going on.
This was the thrust of revelations by a woman called Regina Louf, who told police of child sex parties involving judges, politicians, bankers and members of the royal family. But her stories of sadism, bestiality and murder have been widely dismissed as deranged fantasy.
The fourth defendant, Michael Nihoul, a 62-year old alleged con man and well-known figure at a Brussels sex club, is expected to loom large in this context. Nihoul denies supplying ecstasy pills to Dutroux and Lelievre in exchange for Laetitia Delhez.
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