A trial is a well-regulated search for the truth. It is a fact-finding mission where jurors are called upon to answer a question: do they believe beyond a reasonable doubt that the person on trial is guilty of the crime charged? Their answer depends upon the information provided to them during the trial by both sides. The rules of evidence filter witnesses, testimony, and exhibits from being entered into evidence and therefore considered by jurors.  Thus, it is not entirely accurate to say that a verdict in a particular case was based on all facts, circumstances and witnesses to a particular crime. It is more accurate to say that a verdict is based on all facts and circumstances that were admissible in the trial.