I read an article a while back that I think was to do with the AAIB, and that said the Public's perception of what they heard or saw can actually be better than that of an "expert" witness, be it Pilot or Engineer. Simply because they have no preconception or knowledge of what is happening, so they tell it in their own words what they heard or saw, and that can be more accurate in certain incidents.
Indeed. It was interesting that the AAIB quoted a civilian witness in their interim report into the Clutha Bar crash.