The roles of a judge are to preside over legal proceedings at his assigned courtroom, to determine whether the evidence presented is legally admissible, to give the jury instructions on the law it should apply to return a verdict and to decide sentencing in criminal procedures. Additionally, a judge may function as the sole fact-finder in cases where the participants waive their right to a jury.
The rules of civil and criminal procedures of each jurisdiction usually outline the specific duties and powers of a judge within that jurisdiction. In the federal courts of the United States, these procedures are outlined in the Federal Rules of Civil Procedure, Federal Rules of Criminal Procedure, Federal Rules of Appellate Procedure and Federal Rules of Evidence.
At the federal level, judges have a limited jurisdiction, including cases arising under the U.S. Constitution and other federal laws, as well as cases between parties of diverse citizenship where the amount in controversy exceeds a certain amount. These judges administer the different steps of every cause of action and are able to make legal rulings - known as summary judgments, judgments as a matter of law and judgments on the pleadings - when there are no factual matters in dispute.