 During the trial itself, which took place in October 1938, his testimony was impeached by the defence using the accusations of seeking to make money and fame from the case, as well as allegations of witness tampering and even taking a bribe from Greibl.The allegations did not stand up, but the FBI thought Turrou had made the organization look amateurish, unable to defend the nation against espionage.During his investigation, Turrou used polygraph tests to interview his suspects, perhaps the first of its use by the FBI in an espionage investigation.