In assigning culpability the justice system does not go to a legal action in a sequence of events and speciously use it to create cause and effect. Rather it finds the action NOT reasonably supportable as an action or response. Oh, wait, EVERYBODY knows that...
Getting out of ones car is not a crime. Either is following someone in public. Using a but for analysis, why didnt the officer conclude that had Trayvon not smacked Zimmerman, he would still be alive? That appears to be a far more immediate cause of the shooting than Zimmermans getting out of his car.
Its also an unsupportable theory for criminal liability. How far back do you go? One could say if Zimmerman stayed home that night and didnt go to the store, Trayvon would be alive. Or if Trayvon had stayed home and not gone to 7-11 that night, he would still be alive. But for a hundred things, Trayvon would be alive. (If only an airline passenger had taken a different plane, he wouldnt have gone down with the flight. If only a person took a different route to the store, or left home 10 minutes later, he could have avoided a fatal car accident and would still be alive.) They are all true, but they are not a basis for charging a crime.
http://www.talkleft.com/story/2012/5/17/221353/149