Unfortunately the AAIB rarely if ever link an accident with the pilot's history of previous fruitcake-type behaviour.
It's a pity because yet another trusting passenger has paid the price for this policy of silence.
And cowboy behaviour is rarely going to be a very isolated thing, in a particular individual.
It underlines the need for some care before just flying off with somebody. But thankfully this kind of thing is very rare in GA. Just as well, since there isn't much one can do if the said pilot moves around when renting, and nothing at all can be done if he is an owner.
What is less rare is crap maintenance...