Scotland has a 'Not Proven' verdict as a third option. That could well have been the decision of the jury here, had they that option.Posted by Seikou-Kishi (here)
The verdict was "just" in that the prosecution could not prove (beyond a reasonable doubt) Zimmerman acted other than in self defence.
That doesn't mean he did act in self defence, just that the prosecution doesn't have the means to demonstrate to the contrary.
http://en.wikipedia.org/wiki/Not_proven