@Motnight
Why did husky voice sister crash the car? Was she trying to kill them both?
Yes, what was the point of crashing the car? By no means certain that it would be sufficient to kill either or both of them?
So much woolly thinking in the plotting of this 'drama'. It was like they started out filming just 'this is what happened' with then went back and made up odd bits on the fly to try and cobble together a mystery.
And I said exactly the same as other about the badge at the graveside scene! As if she would have had that key piece of evidence and how crass to hand it to the mother with a 'aw shucks' shrug!!