I agree. According to the Smiths he was walking normally with his daughter held against his shoulder. The only slightly odd behaviour was his refusal to acknowledge the Smiths and Mrs Smith in particular and the way he looked down when passing them.
Had Smithman been up to no good however I don't think he would have gone anywhere near the Smith group. Given there were nine of them including several children they must have been heard before they were seen giving Smithman the opportunity to veer off.
Smithman could be yet another red herring?
I don't think they would have been particularly noisy, John. They were split up.
Peter and his family were walking ahead - his children were aged 13 and 6 and his nieces aged 10 and 4; his wife was feeling unwell and there is no suggestion the children were running about playing.
His parents were walking a distance behind and Aoife was walking on her own behind them.
I don't think it is particularly odd that he did not acknowledge Mrs Smith's greeting. If he was an English speaker, he may have thought she was making a statement of the obvious; his brisk gait indicated he was anxious to reach his destination.
He may not have heard or may not have realised the comment was directed at him.
He may not have understood if English was not his first language. Or he may have just been one of those people who do not acknowledge a stranger's greeting.
Neither do I attach any significance to him looking down as noted by Mr Smith. He may not have been 'hiding' his features. He was walking downhill carrying a burden, it makes sense every so often to look down to check one's footing.
I tend to agree that smithman is indeed a red herring.
One thing which does puzzle me is why the thirteen year old was interviewed in Eire but while the twelve year old returned to Luz to participate in the family reconstruction of events, he did not.