Burden of Proof
Beyond a Reasonable Doubt
Burden of Persuasion
While the prosecution has the burden of proof in criminal cases on almost all issues, the defense has the burden of persuasion. The defense does not have to prove that the defendant is innocent, but it must persuade the jury that the prosecution has not established the defendant's guilt beyond a reasonable doubt. this can be done by discrediting prosecution witness and/or calling defense witnesses.
Trier of the Law
The role of the trier of the law is to decide what law applies to a given case. This includes giving the jury instructions on the definitions of the [crime(s)] charged, ruling on objections made at trial (such as hearsay), and deciding whether Miranda and search and seizure rules were correctly followed by the police. In a trial, the trier of the law is the judge.
Trier of the Facts
The role of trier of the facts is to evaluate the evidence and decide which facts have been sufficiently proven. In a jury trial, the jurors are the triers of the facts and the judge is the trier of the law. In a trial without a jury, the judge is both the trier of the facts and the trier of the law.
Federal Rules of Evidence