So suppose a woman is walking alone along a dark road.

[ctaylors6]

111. I think the man would probably be guilty

IMHO applying the reasonable person standard in the case of deadly force being used (him shooting her), it would not be reasonable that a man responded to being sprayed with mace and hit with her purse by shooting her. I suspect that if he had punched her, even more than once, and she died from the injuries, that might be a different result than if he shot her.

I really think that it's helpful to separate the burden of proof issue from the reasonable person/self-defense issue. If you saw someone being straddled on a sidewalk or street, yelling for help, unable to get up, and getting their head repeatedly pounded into the sidewalk, you could very reasonably fear that person was being inflicted with great bodily harm or even death.

Whether you believe that this is the situation Zimmerman was actually in, especially coupled with how you might feel about how the confrontation started in the first place, is an issue of proof. I assume the state's position was that Martin was on the bottom and/or Zimmerman wasn't really being hurt enough to fear for his life. The defense's position was that Zimmerman was on the bottom, couldn't get up, and thought he could die from the "pound and ground." The jury had to believe the state's position beyond a reasonable doubt for Zimmerman to be found guilty (assuming the jury thought the elements of murder or manslaughter were met.)