anotheroldgit. Just to correct you there. Every traffic department in every constabulary (or RDP, Road Polising Division) have a AIU or CIU which stands for Accident (or crash) Investigation Unit. at every serious or fatal accident they are duty bound to attend 24/7. Further, any fatal road crash is dealt as a potential crime scene until proved otherwise. Mush the same as any sudden death.
And on a further point, if there are huge amounts of insurance revenue to pay out i canb assure you the cars (after Police forensic tests) are meticulously jigsawed back together.
And finally, more and more cars, both domestic and certainly company cars, are having an equivelent of a black box fitted.
So I am afraid with your post, you have been misinformed.