What did the German chancellor's office know? That's what's a parliamentary investigative committee is looking into as it conducts its final public interviews in the aftermath of the the whistleblower Edward Snowden's 2013 revelations that the US's National Security Agency (NSA) had spied on German and EU citizens - including Angela Merkel - with the cooperation of the foreign intelligence service, the BND.

On Monday, the committee questioned the state secretary for intelligence affairs in the chancellor's office, Klaus-Dieter Fritsche, for over four hours. In some respects, the session was a warmup for Thursday, when Merkel herself will appear before Bundestag deputies. All indications are that she's in for a rough ride.

"So, who dropped the ball?" committee chairman Patrick Sensburg, a member of Merkel's conservative Christian Democrats, pointedly asked Fritsche. "My impression is that our conglomeration of search terms wasn't adequately maintained at all."