The car behind who rear ends the car in front has a presumption of being at fault, but if there is evidence to show the car in front caused the accident (say, b

The car behind who rear ends the car in front has a presumption of being at fault, but if there is evidence to show the car in front caused the accident (say, by brake checking them) then that can change the outcome. Before dash cams, it was very rare for the car behind to be able to show any proof otherwise, so they were usually at fault unless there were credible witnesses of the brake checking. But no, you can't just randomly threshold brake in the middle of the highway for no reason and expect to blame the car behind for your actions (or the actions of your car).