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Legal Research: A Guide to Case Law

Case law is law based on judicial decisions. This guide cites resources for locating and identifying judicial decisions from the U.S. courts using primary and secondary sources of case law.


Each branch of government produces a different type of law. Case law is the body of law developed from judicial opinions or decisions over time (whereas statutory law comes from legislative bodies and administrative law comes from executive bodies). This guide introduces beginner legal researchers to resources for finding judicial decisions in case law resources. Coverage includes brief explanations of the court systems in the United States; federal and state case law reporters; basic Bluebook citation style for court decisions; digests; and online access to court decisions.

Court Systems and Decisions

U.S. Supreme Court

One court that creates binding precedent on all courts below.

U.S. Courts of Appeals

Thirteen circuits (12 regional and 1 for the federal circuit) that create binding precedent on the District Courts in their region, but not binding on courts in other circuits and not binding on the Supreme Court.

U.S. District Courts

Ninety-four districts (1 district court and 1 bankruptcy court each) plus the U.S. Court of International Trade and the U.S. Court of Federal Claims. District Courts must adhere to the precedents set by the Supreme Court and the Circuit Court of Appeals in which they sit.

Hierarchy and precedence in the federal court system.


The United States has parallel court systems, one at the federal level, and another at the state level. Both systems are divided into trial courts and appellate courts. Generally, trial courts determine the relevant facts of a dispute and apply law to these facts, while appellate courts review trial court decisions to ensure the law was applied correctly.

Stare Decisis (Precedent)

In Latin, stare decisis means "to stand by things decided." In the U.S. legal system, this Latin phrase represents the "doctrine of precedent, under which a court must follow earlier decisions when the same points arise again in litigation." (Black's Law Dictionary, 11th ed.) Typically, a court will deviate from precedent only if there is a compelling reason. Under "vertical" stare decisis, the decisions of the highest court in a jurisdiction create mandatory precedent that must be followed by lower courts in that jurisdiction. For example, the U.S. Supreme Court creates binding precedent that all other federal courts must follow (and that all state courts must follow on questions of constitutional interpretation). Similarly, the highest court in a state creates mandatory precedent for the lower state courts below it. Intermediate appellate courts (such as the federal circuit courts of appeal) create mandatory precedent for the courts below them. A related concept is "horizontal" stare decisis, whereby a court applies its own prior decisions to similar facts before it in the future.

Case Law Reporters

Decisions are published in serial print publications called “reporters,” and are also published electronically. Reporters are discussed in greater detail under "Federal Court Decisions" and "State Court Decisions." Information about how to cite decisions in a reporter is discussed under "Citations."