As someone who has a job and family, there are times when you're in a rush. It's never a good idea to tailgate another vehicle, but if you're attempting to pass, you might have to get close to the vehicle to get ahead of someone in another lane before you can merge.
Some people don't take kindly to others getting too close to them. Most people would move out of the way, but some people become enraged and brake check the other vehicle.
Brake checking is an illegal action. The person in front of you, in a brake checking situation, suddenly slams on their brakes. They do this to surprise you, and sometimes it's to intentionally cause a collision. Regardless of where you are, this action puts you and others in danger.
Rear-end collisions aren't always the fault of the rear driver
There is a myth that the car in the rear is always at fault when they get into a crash with the vehicle that is in front of them. The reality is that either driver could be at fault. If you have a dash cam in your vehicle, for example, showing the authorities that the other vehicle was stopped suddenly and for no reason could be enough to have the other party held liable for the crash.
Brake checking is a kind of road rage. Road rage in itself is illegal, because it is a form of reckless driving. Someone who recklessly controls their vehicle and intentionally puts others at risk should not be on the roads.
How can you prove the other driver brake checked you?
In crash scenarios, there are many times when it's witness statements that help the most. If someone at the scene who agrees that the other driver suddenly cut in front of you and stopped, or that the driver had no reason to suddenly brake but did so anyway, their statement will help you. It would also be helpful to obtain any video evidence you can, which would support your claim that the other driver stopped without regard for the safety of those around them.
Videos are also great if you can get the other driver to admit to brake checking you. For instance, if the driver gets out of their vehicle after the crash and tells you they taught you a lesson, then that would be like an admission of guilt and helpful for your case.