The cops saw somone beating the **** out of you. Perfectly legal
The cops saw you punch someone. YOU MUST BE KILLED
Playing GTA Vice City
Driving a car down the road really fast
See a cop cross the road, and I'm going to hit him!!!
Reflexively, I jump out of the car
Car smashes into the cop, and goes hurtling down the road, before hitting a T-Intersection and rides up onto the footpath, knocking over a light-pole and killing a whole heap of pedestrians
Didn't get into trouble because I wasn't in the car