This is off topic, but a question I don’t hear people ask in regard to the Zimmerman case is: why didn’t any of the several people hearing screams intervene to stop the brawl? Never mind who was screaming, no one felt an obligation to intervene. Eye-witness John Good came out and said something like “stop” but then immediately ran back inside. Others could be heard saying, “don’t go out there”. I don’t say they should have joined the fight, but if a few people had gone outside and screamed or blew a whistle it probably would have been effective.
(I’ve been in such situations twice.)
Error Statistics Philosophy 
I did follow the testimony as it unfolded. The testimony is, as you probably know, available on Youtube. A quick look at some contemporaneous news accounts describe’s Good as stating that he heard noises, investigated, saw a scuffle, yelled to the combatants to stop, and went to call 911, when he heard the gunshot. His testimony supported GZ’s account that Martin was on top of him, and beating him.
Now Good did not know that there would be a gun fired, and you might well ask why did he just shout to stop, rather than running out and separating the two people. Still, his actions, while not heroic, were not totally unreasonable.
Interestingly, we could say that Good’s decision not to intervene directly was the “but for” cause of the shooting. The law generally requires “but for” causation PLUS a vague concept called “proximate causation,” which is not always proximate in the sense of close.
Nathan: Yes, and GZ says he told Good the police were already on their way, that he should help him instead. Something like that. So, in a sense, legally, you’re saying, Good was a cause? Of course there were other people too.
Fear of injury, hesitancy to get involved. MYOB.
Little bit of irony? Zimmerman emerges from hiding to rescue a family from an overturned vehicle last week! (even as he was being villified—it is like a Tom Wolf novel). http://hotair.com/archives/2013/07/22/stranger-than-fiction-george-zimmerman-emerges-from-hiding-to-rescue-victim-of-car-accident/
George the Good Samaritan:
http://legalinsurrection.com/2013/07/zimmerman-briefly-emerges-from-hiding-to-help-rescue-family/