In case law, a test case is a legal action whose purpose is to set a precedent. Test cases are brought to court as a means to provide a clearer definition to laws with disputed meaning and/or intent. An example of a test case might be a legal entity who files a lawsuit to see if the court considers a certain law or a certain legal precedent applicable in specific circumstances. This is useful, for example, to validate later filing similar lawsuits.
Government agencies sometimes bring test cases to confirm or expand their powers.
Examples of influential test cases include:
- Plessy v. Ferguson (1896)
- Tennessee v. Scopes (1925)
- United States v. One Book Called Ulysses (1933)
- Brown v. Board of Education (1954)
- Griswold v. Connecticut (1965)
- Oneida Indian Nation of N.Y. State v. Oneida County (1974)
- Adams v Cape Industries plc (1990)
- Mabo v Queensland (No 2) (1992)
- National Westminster Bank plc v Spectrum Plus Limited (2005)
- District of Columbia v. Heller (2008)
- Case of first impression
- Leading case
- Uncommon Law, or Misleading Cases in the Common Law, by A. P. Herbert; still further misleading case
- In FTC v. Dean Foods Co., the FTC sought to establish its power to obtain preliminary injunctions in anti-merger cases. In FTC v. Sperry & Hutchinson Co., the FTC sought to establish its power to invoke section 5 of the FTC Act, 15 U.S.C. sec. 45, against business practices that were "unfair" without being similar to antitrust violations. In United States v. Glaxo Group Ltd., the Justice Department sought to establish its power to invalidate patents even though they were not procured by fraud. Unsuccessful such test cases sometimes provide a basis for convincing Congress of the need for corrective legislation.