Here is a question I received and answered on the now-defunct website AllExperts.com:
Are skid marks darkest at the end or beginning? And can you determine the tread from the tread marks? My daughter was in an accident and the cop cited her even though from his pictures it looks like the skid marks are in the opposite direction, and she never even applied her breaks because her car died on impact. If they are the darkest at the end that would prove they are not hers, Besides the fact they curve the opposite direction that her vehicle traveled. I asked about the tread marks because she has a very unique tire tread and blowing up the photos show they don’t match her tread.