Car in front slams on breaks (interstate) for no reason and gets rear ended-vehicle behind is boxed in-who is at fault?

Question

Car in back had vehicles on either side (3 lane interstate)/could not move over and slammed on breaks, but cracked the bumper of car in front (crushed front end of car in back).  Car in front had no reason to stop in regular 65mph traffic.  Car in back received a ticket for failure to stop and full fault (nailed by future insurance).  I was under the impression that the front vehicle, with no reason to stop, would hold partial fault (as in, even if a deer is on the interstate you are supposed to hit it instead of stopping and potentially getting hit by someone else/putting others in danger-and there was nothing on the road-vehicle in front was technically driving at less than 40mph in the middle lane of a 3 lane interstate).

Tim Akpinar · Answer

The standard rule in most rear end collisions in virtually any jurisdiction is that the vehicle in the rear is at fault. Vehicle & traffic law can vary from state to state, and highway safety officers at the scene could characterize things differently, whether citing the situation as following to closely, failure to leave safe distance, maintaining an unsafe speed, etc., based on selections listed in the backside of the standard police report. But the basic premise doesn't usually change, barring extenuating circumstances. Depending on evidence, your insurance adjuster might attempt to mitigate damages by using your account of the lead vehicle's slow speed. Good luck 
 
Tim Akpinar

Q: Car in front slams on breaks (interstate) for no reason and gets rear ended-vehicle behind is boxed in-who is at fault?