[Kell]

It's because in France and Belgium we have a category, called "Magistrat" that contains both the judges (independent, neutral etc.) and the prosecutors (neither independent, nor neutral). So we often discuss it saying that judges are neutral magistrates. Sometimes this is lost in translation :).

Edit : And the Juge d'Instruction IS a special judge, because he doesn't judge anything, his job is to head all investigations in serious and complicated cases. Normally that would be the prosecutors job... so it's an independent and trully neutral man (a judge) doing a prosecutor job, in the interest of the accusation and the defense, at the same time. That's quite special.