Defences
Wingsfolded,
You are quite correct, the matter is decided, and by French courts. That is a final matter. French courts are aligned on the principle of establishing fact not guilt, so they have established the facts of the accident.
However, I offer my comments in the context of making some sense of the judgement, and as this is a forum for doing exactly that. There are no absolute villains in this accident, and as it seems, no malicious intent at all, that leaves Mr Reason's cheese. Unfortunately the holes are not too many in number in this accident.
Whilst the term "frolic of one's own" is an English legal term it will do for a reference point for culpability, a legal concept that transcends national boundaries. it is a matter of degree, which is open to discussion.