The series is called 'Lie to Me' with Tim Roth in the starring role. It purports to demonstrate the micro-expressions we use when we're trying to not be too overt in our responses to situations. Covering up guilt, lies, anger, or even suppressing happier but perhaps inappropriate reactions to issues (like trying not to smile when told your horrible husband's just been snuffed, and left you £3m). The shift of eyes to the left (the imaginative part of the brain) is supposed to indicate a lie, or at least not the whole truth. A downward glance can be guilt or shame, and Fallon manages to do both for a fleeting nano-second in his reply to that rather convoluted question, DO. Upward glances and especially to the right indicate a search of the memory, or thinking, area of the brain, for example if you're asked to recall a detail from some time ago. Surprise yourself one day by noting when you do that!
The programme is quite fascinating and I must say that the tiny, almost imperceptible expressions, which only an expert face reader might catch, do seem to ring true. I think it's likely that Fallon doesn't feel remorse for any hurt he's caused anyone, and I also think that the finale, where Clare asks whether he's likely to repeat the behaviours, is quite telling - it's almost a "Well, you know me - I might, I might not" response. As for whether he's still consorting with all those 'wrong people', who knows for sure, but it'd be difficult to kick them all into touch in one go.