Fourniret appeared in a glass-enclosed defendants' box alongside his wife and refused to speak at the opening of his trial unless the judge emptied the courtroom.
Fourniret was detained by Belgian police in June 2003 after his attempted kidnapping of a 13-year-old girl went wrong.
The girl gave authorities his licence plate number after she managed to unbind her hands and escape from the back of his van.
Belgium extradited Olivier to France in 2005 and Fourniret in 2006.
The trial, one of France biggest murder trials, has drawn comparisons with that of the 2004 trial of Belgian Marc Dutroux, who was convicted of killing six girls between 1995-6.