So your best bet is to get ahead of it and make sure it's the other guy.

Where it's the same insurance, stakes are probably low as far as they're concerned. They'll pay for it either way. But short of this being a situation of someone sliding off the road due to snow or ice, or having a tree or rock fall on the car - either your wife or the other guy is going to take the hit of being responsible.

Police are getting out of the assigning blame business. If someone ran a stop sign or red light and it's obvious, they may give a ticket. But most fender benders on the freeway of someone rear-ending someone else results in the police not assigning blame - they let the insurance companies fight it out.