The list of legal reasons to exclude evidence from a jury is very long. Many, many times, judges preside over criminal trials with the full knowledge that the defendant did in fact do what he (or she) was accused of.
A lot of people focus on the fact that a judge can disallow evidence provided by the prosecution… but they seem unaware that judges can, and do, also disallow evidence provided by the defense. It is an unfortunate fact of our trial system in the U.S. that judges have a great deal of power to influence the verdict to produce the outcome they want, by what evidence they allow and disallow.
A lot of people focus on the fact that a judge can disallow evidence provided by the prosecution… but they seem unaware that judges can, and do, also disallow evidence provided by the defense. It is an unfortunate fact of our trial system in the U.S. that judges have a great deal of power to influence the verdict to produce the outcome they want, by what evidence they allow and disallow.