Courts are required to follow the decisions of higher courts in the same jurisdiction. Accordingly, cases which are both (1) from a higher court, and (2) in the same jurisdiction are considered mandatory authority.
All courts, federal and state, are bound by the decisions of the U.S. Supreme Court on U.S. Constitutional and other issues of federal law.
In the federal courts, circuit courts tend to follow decisions previously issued within that circuit. Moreover, each district court falls under the jurisdiction of a circuit court, and the opinions of that circuit court will be binding on that district court. For example, the 9th Circuit is the federal circuit court for California, and the Central District of California is the federal district court for Los Angeles. Accordingly, 9th Circuit opinions are binding in the Central District of California.
State courts are typically bound by the decisions issued by the higher courts in that state. For example, California trial courts are bound by the opinions issued by the California courts of appeals and the California Supreme Court. However, California courts are not bound by the decisions of other state courts, such as Arizona.
Finally, it should also be noted that state court decisions typically control on substantive issues of state law. You may have a federal court case with a state law issue. For the substance of the state law issue, decisions of the state supreme court would be binding, even though you are in federal court. Decisions of the state court of appeals may also be useful, but the federal courts might treat that as persuasive authority.
While it is always best to cite to controlling authority, sometimes it can be useful to cite to non-binding cases as relevant persuasive authority. For example, if there is little or no binding authority for your issue in your jurisdiction, you may want to cite to on-point cases outside of your jurisdiction.
When citing cases that are merely persuasive, rather than binding, it is important to explain why the court should follow that precedent. Such explanation may include:
Moreover, persuasive authority can be used as a tool to find cases that are binding. For example, if you are in the 9th Circuit, and you have found a relevant 5th Circuit case, you can use the 5th Circuit case to find 9th Circuit authority by following the techniques for headnote and citing reference searching discussed in the Caselaw Searching section.