inconclusive evidence gets a not guilty verdict under the law
Juries don't need conclusive, with 100% certainty, evidence to find a guilty verdict. They need sufficient evidence, to lead them to believe, beyond a reasonable doubt
, that he is guilty as charged.
Juries evaluate evidence and connect the dots--they are expected to think. If we had all crimes videotaped, and witnessed, so that there were no doubts or questions about what took place, in anyone's mind, we really wouldn't need juries or trials to determine the facts or the verdict. In our legal system, the jurors are the "finders of fact"--it's what they conclude
from the evidence they are presented that determines the verdict.
the law instructs the jury to believe Zimmerman unless they have evidence to the contrary
And inconsistences in his statements to police, or contradictory evidence, calls his credibility into question, particularly if there is no supporting evidence, or if that evidence is weak. If the jury has questions about his credibility, based on such things, they don't have to believe him. Zimmerman's credibility is a major factor in this case.