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Northern Illinois University
College of Law
David C. Shapiro Memorial Law Library

Basic Legal Research

Types of Case Law

Case Law & Common Law:

When dealing with case law, you will often hear the term "common law." Common law is case law that creates law. The Court's decision is the controlling law in a common law issue.

There are several areas of law (e.g., torts, contracts) where there is no statutory law governing most of the relevant issues. Common law (also called judge-made law) is used in these areas.

Common law develops and changes over time:

  • A dispute comes before the court and a decision is made.
  • Later, another dispute on a similar issue will come before the court, and that court will look to earlier decisions (precedent) for guidance.
  • If the case before the current court is virtually identical to the earlier case, a similar ruling to the earlier case will likely result.
  • If there is some type of distinguishing factor from the earlier case, a different result is possible.

Each new decision adds a piece to the body of common law. Because of how common law develops over time, it may be necessary to look at very old decisions to understand the current state of the law.

Case Law & Statutory Law:

Not all case law is common law. The other type of case law you will encounter is that which interprets a statute.

  • When the legislature enacts a statute the language is not always clear. Cases involving statutes may be brought into court in order to clarify ambiguities or interpret clauses in the statute.
  • The court looks at the statute, interprets it, and applies the law/interpretation to the case at hand.
  • The appellate court's review of these decisions provides the case law that is published along with the statutes in the annotated codes.

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