Comment by jcranmer

The fundamental idea of a jury, when it comes down to it, is that you're asking 12 random people "was this person's actions reasonable?" given conflicting accounts of what those actions were. The process by which you get there is more convoluted than that (and generally assumes a higher competence by the jury than probably exists), but juries seem to do a very good job of upholding the basic idea of evaluating the reasonableness of actions.