AA,
Along that line of thinking....perhaps the Coppers should do a time line analysis and determine if the victim exceeded the speed limit during his cross country drive to the airfield where the mishap occurred. If they determine he was in a "hurry" to get there and violated the speed limits then it would show he was not coldly going to have a civil conversation and would therefore show his state of mind was not that of a normal person.
I will bet you the Defense will be doing that along with other investigations to fully define the situation that existed prior to the Prop Strike. The Police should have done that already and not just look to prove a crime without taking in all of the evidence that both supports and mitigates the charge.
I would suggest if the man is charged with Murder and the charge is proved in a court the taking of money for the flying will become a rather moot point.