A precedent, with regard to law, is a specific legal case that typically sets a standard for how similar cases should be ruled based on the initial case. In other words, it is a legal case that establishes a basic sense of how an issue can be handled, and subsequent cases will often rule in a way that is similar to the precedential one. There are typically two major types of precedents in law: binding ones that usually must be followed by other courts in most situations, and persuasive ones that can be followed but are not mandatory. A precedent can be an important part of a legal issue, but there is some criticism regarding their and importance in American law.
The concept of a precedent in law stems from English common law and was transferred from the legal system of England to American law. The binding or mandatory type is one that must be followed by other courts, and is usually established by a higher court. In the US, for example, binding precedents are often established by the US Supreme Court and all lower courts are expected to uphold the rulings.
A persuasive precedent, on the other hand, is one that is established in a legal case but that does not have to be followed. These typically serve as examples for what has been done before, and what others may consider as a legal issue moves forward. If a tobacco grower was found culpable in a wrongful death case involving someone dying from lung cancer caused by smoking cigarettes, for example, unless the case was settled in the highest court it would serve as a persuasive precedent for cases that followed it. Other courts could rule differently on similar cases in the future, but the one case would establish grounds for other courts to follow suit.
Precedents are often used in a number of different ways by lawyers and legal critics. Students of law will often read them to learn about what has come before, and to get a sense of what is likely to follow. A precedent can often indicate how future courts might rule on a particular subject, or the importance of a particular subject at any given time. There is a fair amount of criticism, however, with regard to the use of precedents in American law. Some have argued that they can too often cause courts to rule in a way that is uniform with what others have done, regardless of the facts of an individual case.