France's top terror judge says Europe's combustible mix of experienced extremist fighters and young jihadis looking to join the fighting in Syria poses new dangers for a continent ill-equipped to trace hundreds of newly radicalized people.

Marc Trevidic has handled French terrorism cases since 2006, but has recused himself from investigating the Jan. 7-9 attacks that left 20 people dead. Victims included Trevidic's former police bodyguard, who had been assigned to protect the editor of Charlie Hebdo and was among the first to be killed. Three days of terror ended when three gunmen died in standoffs with security forces.

In an interview with The Associated Press, Trevidic says the veteran fighters "are small in number, but in quality it's another problem."