Unfortunately, as far as evidence goes, the crush damage on the two cars is going to be the most influential factor. There are probably no skid marks on the road (because of the rain)but maybe there are some gouges in the pavement (from flattened tires, or other metal parts of cars). Debris has probably been kcked around too much to matter now, either. Go back to the scene, and take as many pics as you can, especially of the above mentioned items. Think CSI!
Witnesses are so VERY important. If you ever get in a crash, especially a red light case, make sure that you stop a car and get that persons name and number. It will save you so much grief in the future by helping the crash investigator determine fault. This is to be the number one priority after you determine that everyone is ok.
It is sickening to see how people will lie, cheat, and sell their souls during a crash investigation.
