A bright-line rule (or bright-line test) is a clearly defined rule or standard, composed of objective factors, which leaves little or no room for varying interpretation. The purpose of a bright-line rule is to produce predictable and consistent results in its application. The term "bright-line" in this sense generally occurs in a legal context.
Bright-line rules are usually standards established by courts in legal precedent or by legislatures in statutory provisions. The US Supreme Court often contrasts bright-line rules with their opposite: balancing tests (or "fine line testing"), where a result depends on weighing several factors—which could lead to inconsistent application of law or reduce objectivity.
In the United States, there is much scholarly legal debate between those favoring bright-line rules and those favoring balancing tests. While some legal scholars, such as former Supreme Court Justice Antonin Scalia, have expressed a strong preference for bright-line rules, critics often argue that bright-line rules are overly simplistic and can lead to harsh and unjust results. Supreme Court Justice Stephen Breyer noted that there are circumstances in which the application of bright-line rules would be inappropriate, stating that "no single set of legal rules can ever capture the ever changing complexity of human life."[1]
Miranda v. Arizona (1966) may be considered establishing a bright-line rule. The majority opinion in that case required law enforcement agents to give a criminal suspect what is now known as a Miranda warning of their "Miranda" rights when the suspect is in custody, and when the suspect is about to be interrogated.
The Taxation (Bright-line Test for Residential Land) Act 2015 is a form of Capital Gains Tax legislation in New Zealand.[2] When it was introduced a bright-line test was described as, "a term used in law for a clearly-defined rule or standard, using objective factors, which is designed to produce predictable and consistent results."[3]
