"Of course there are security flaws. If there weren't, an organized terrorist attack of that level wouldn't have occurred."
That stark assessment comes from Judge Marc Trevidic, who spent 10 years leading counterterrorism investigations for the French national courts.
Trevidic, who left the post last summer but remains part of the French judiciary, has told national media in the wake of the Paris attacks that the biggest problem facing law enforcement agencies in his country is the overwhelming amount of work on their plates.
"They are simply overloaded... we've got security services who have been hiding the fact that they could no longer cope," Trevidic told France Inter, part of France's public radio network.
He said attacks and planned attacks that have been thwarted -- dozens this year alone, according to officials -- have been stopped "by pure luck."
"On the whole, during the last few years, we realized that we are not coping anymore," he said of France's intelligence agencies. "Those who were really under surveillance... we were not even able to stop them from going to Syria... we couldn't stop them from coming back."
Trevidic's remarks come amid indications that European security agencies -- particularly in France and Belgium, missed a series of red-flags which could have led to greater scrutiny of the suspects in the attacks that left 130 people dead in Paris.
Several of the nine suspects had been flagged to French agencies by Turkey or other nations, and the man believed to have planned the attacks, Belgian national Abdelhamid Abaaoud, bragged earlier this year about being able to move freely between Syria and Europe.
CIA Director John Brennan has also pointed to the sheer quantity of individuals in and from Europe who warrant surveillance as being a major challenge for America's allies.
Between 300 and 500 people from Belgium alone -- the most per capita from any European nation -- are believed to have travelled to Iraq and Syria to join the fight with ISIS and other groups. Hundreds more have travelled from France.
The interview with Trevidic highlights the fact that agencies in his country and others are struggling to get a grasp on how many of those people have returned, and what they're doing once they do come back.
French television network BFM TV reported Monday, citing a judicial source, that judges had issued 235 indictments in connection with 99 separate criminal investigations into suspected French jihadists who've travelled to Iraq and Syria.
So far, French prosecutors have secured 11 convictions in those cases, said BFM, adding that only 10 of the proceedings are actually related to attacks or attempted attacks on French soil.