Assume polygraphs are 96% accurate and 5% of men have affairs. The polygraph says Samuel is lying when he claims he doesn't cheat. What are the odds he is lying?

I am very confused by this problem, because it feels to me that the 5% statistic is a red herring. If the polygraph determines lying or truth-telling accurately 96% of the time, isn't that the only statistic we need?

It would be a different question if the question was what the odds would be that the polygraph would say he was lying.