I agree.  George does know whether or not he told the truth. He may have told the truth or he may have lied.
He just claims he was telling the truth.

Agent Trimarco and Mr. Youngblood detected that he was lying on one exam and cheating on another. They can articulate their reasons. Their jobs and careers were not at stake. I see no motivation for them to lie about their conclusions.

If Dr. Maschke lied on his exams he would certainly have motivation to deny it.

Which brings one back to the question of credibility. I choose to believe the guys who DID NOT have a stake in the outcome of the exams or write a book that attempts to justify lying and cheating if they think it might help them get a job with the government.

Sancho Panza