Yeah, that was an error of judgement, a well known tactic to implicate a person, ask them a question and allow them to lie, then use that against him.
Perhaps he wasn't aware as most people are, but once you are caught out, whether it's at work or in politics and you know it's probably going to lead to a disciplinary hearing, you don't have to answer any questions regarding the matter, your superior cannot fire you for refusing to answer, it's either they charge you and you answer there or nothing happens.
He should have asked for time to consult and then someone would have advised him, but people make the mistake of thinking the conversation you are having with your superior is done in confidence, tell me the truth so that I can help you, it isn't.