Even before legislatures met to make rules for society, disputes happened and judges decided them. In England, judges began writing down the facts of a case and the reasons for their decision. They often resorted to deciding cases on the basis of prior written decisions. In relying on those prior decisions, the judge would reason that since a current case was pretty much like a prior case, it ought to be decided the same way. This is essentially reasoning by analogy. Thus the use of precedent in common-law cases came into being, and a doctrine of stare decisis (pronounced STAR-ay-de-SIGH-sus) became accepted in English courts. Stare decisismeans, in Latin, “let the decision stand.”
Most judicial decisions that don’t apply legislative acts (known as statutes) will involve one of three areas of law—property, contract, or tort. Property law deals with the rights and duties of those who can legally own land (real property), how that ownership can be legally confirmed and protected, how property can be bought and sold, what the rights of tenants (renters) are, and what the various kinds of “estates” in land are (e.g., fee simple, life estate, future interest, easements, or rights of way). Contract law deals with what kinds of promises courts should enforce. For example, should courts enforce a contract where one of the parties was intoxicated, underage, or insane? Should courts enforce a contract where one of the parties seemed to have an unfair advantage? What kind of contracts would have to be in writing to be enforced by courts? Tort law deals with the types of cases that involve some kind of harm and or injury between the plaintiff and the defendant when no contract exists. Thus if you are libeled or a competitor lies about your product, your remedy would be in tort, not contract.
The thirteen original colonies had been using English common law for many years, and they continued to do so after independence from England. Early cases from the first states are full of references to already-decided English cases. As years went by, many precedents were established by US state courts, so that today a judicial opinion that refers to a seventeenth- or eighteenth-century English common-law case is quite rare.
Courts in one state may look to common-law decisions from the courts of other states where the reasoning in a similar case is persuasive. This will happen in “cases of first impression,” a fact pattern or situation that the courts in one state have never seen before. But if the supreme court in a particular state has already ruled on a certain kind of case, lower courts in that state will always follow the rule set forth by their highest court.