Also known as: common law
Written by attorneys · grounded in primary & secondary sources — see below
The body of judge-made law developed through judicial decisions and custom rather than through legislative enactments.
Logan Lane drove through a residential neighborhood at twice the posted speed limit while texting. His vehicle struck and killed a pedestrian who was crossing at a marked crosswalk. Prosecutors charged Lane with involuntary manslaughter on the ground that his conduct constituted criminal negligence under the common law.
Liam Larson sued Lakeshore Industries for breach of a supply contract seeking $75,000 in damages. Larson demanded a jury trial. The court recognized that the suit was one at common law within the meaning of the constitutional provision preserving jury trials for civil cases exceeding twenty dollars.
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Laura Lewis, a citizen of State A, sued Linden Logistics, a citizen of State B, in federal court for negligence arising from a warehouse accident. The federal judge applied State A's substantive tort rules, including its choice-of-law principles, rather than any independent federal judge-made standard.
Lucas Lee, a resident of County X, filed a petition to adopt his niece after her parents' death. The court required proof of residency under the state's adoption statutes because adoption proceedings were unknown to the common law and therefore rest entirely on legislative authorization.
Leonard Lowe sought to prevent disclosure of counseling records created during sessions with a licensed social worker. The court held that the common law, interpreted in light of reason and experience, recognizes a psychotherapist-patient privilege that protects confidential communications made for diagnosis or treatment.
Landon Long operated heavy equipment near a public sidewalk without posting warnings. A pedestrian was injured when a load shifted. The court measured Long's conduct against the common law, legislative enactments, and general customs that a reasonable person would be expected to know in that community.
Lex communis is the Latin phrase for the common law, the body of judge-made rules developed through court decisions and longstanding custom.
Supporting sources
Federal Rule of Evidence 501 directs courts to apply the common law as interpreted in light of reason and experience to resolve privilege claims unless the Constitution, a federal statute, or Supreme Court rule provides otherwise.
In diversity actions a federal court applies the substantive law of the state where it sits, including that state's common-law rules, rather than creating any independent federal common law to govern state-law claims.
Adoption was unknown at common law and exists only by statute. Therefore jurisdictional rules for adoption proceedings are supplied by state adoption statutes rather than common-law doctrines.
At common law involuntary manslaughter includes an unlawful killing caused by criminal negligence or by the commission of an unlawful act that is not a felony within the felony-murder rule.
…weights of the respective interests involved, with the lessons and examples of medical and legal history, with the lenity of the common law, and with the demands of the profound problems of the present day. The decision leaves the State free to place increasing restrictions on abortion as the period of pregnancy lengthens, so…