I would prefer a system where people that were subsequently found to be making false or fraudulent claims or accusations to avoid liability were massively penalised on the excess and future insurance premiums. This way the system would work as it should and there would be no need to presume anything.
I have been involved in an RTA where the other party went as far as moving the location of the accident to another street to try and make it fit with their account of how my wife was supposed to have driven her car into them! When this was exposed as the lies it was the claim simply proceeded as if nothing had happened. There is no penalty and every incentive to make up these lies and that is what needs to be addressed. If people knew that if they drove like idiots and caused injury or damage then they would without fail be held responsible and heavilypenalised if found to be attempting to evade liability for their actions, then they might think twice before trying it on?