What Is Common Law?

Common law is built from precedent. When a court decides a case, the legal reasoning behind that decision becomes binding on lower courts facing similar facts. Over time, an enormous body of law accumulates from decided cases rather than from a single written code.

The formal principle is stare decisis, meaning to stand by things decided. It gives the system predictability, because parties can look at how similar disputes were resolved and anticipate the outcome.

The name comes from the effort after the Norman conquest to establish law common to the whole of England rather than varying by locality. Royal judges travelled the country deciding cases, and their decisions were recorded and reused.

The system spread with British influence, which is why it now operates in the United States, Canada, Australia, India, Nigeria and many other countries. Each has developed its own body of precedent, though courts still sometimes look to decisions from other common law jurisdictions as persuasive.

Most of continental Europe, Latin America and much of Asia use civil law systems, descended from Roman law and reorganised by the Napoleonic and German codes.

The differences are real though often overstated:

• •Civil law starts from a comprehensive written code rather than case decisions
• •Civil law judges are less bound by previous rulings
• •Common law trials are adversarial, with parties driving the case
• •Civil law proceedings are more inquisitorial, with judges investigating actively

Not everything in a judgment binds future courts. Only the reasoning essential to the decision, the ratio decidendi, is binding. Other observations, however interesting, are persuasive at most.

Courts also have room to move. A judge can distinguish a precedent by identifying a material factual difference, and higher courts can overrule earlier decisions outright. This is what stops the system from being frozen by decisions made in very different circumstances.

No modern common law country runs on precedent alone. Legislatures pass statutes constantly, and where a statute conflicts with common law, the statute wins.

What remains distinctively common law is the interpretive role. Courts decide what statutory words mean in practice, and those interpretations then become precedents themselves. Large areas such as contract and negligence still rest primarily on case law built over centuries.

Common law judgments are long, discursive and often include disagreement, which surprises people used to the short declaratory rulings of civil law courts.

The length has a function. Because the reasoning becomes binding on future courts, judges must set out exactly which facts mattered and why, so later courts can apply or distinguish it. Dissenting opinions are published too, and dissents have occasionally become the majority view decades later, which means preserving the losing argument has real value in a system built on accumulated reasoning.

One case shows how a single decision can create a whole area of law. In 1928 a woman in Paisley, Scotland, drank ginger beer bought for her by a friend and later claimed the opaque bottle had contained the decomposed remains of a snail. She said she became ill. Because she had not bought the drink herself, she had no contract with anyone, and the established law seemed to leave her without a claim against the manufacturer.

When the case of Donoghue v Stevenson reached the House of Lords in 1932, the majority decided that a manufacturer owed a duty of care to the eventual consumer. Lord Atkin expressed this as a duty to take reasonable care not to injure your neighbour, meaning people closely and directly affected by what you do. That neighbour principle became the foundation of the modern law of negligence, and courts across the common law world have built on it ever since.

Early common law courts had real limits. Their main remedy was money compensation, called damages, and they followed rigid procedures. Someone who needed a different result, such as stopping a neighbour from building on their land, could petition the king. These petitions were passed to the Lord Chancellor, and over time the Court of Chancery developed its own body of rules based on fairness and conscience, known as equity. It created remedies the common law courts did not offer, such as injunctions, which order someone to do or stop doing something, and specific performance, which enforces a contract instead of paying compensation.

Equity also produced the trust, in which one person legally owns property but must manage it for the benefit of others. Trusts are still central to pensions, charities and family wealth across the common law world. For centuries the two systems ran in separate courts, and Chancery became notorious for delay, famously mocked in Charles Dickens's novel Bleak House. The Judicature Acts of the 1870s merged the courts so that any court could apply both, with a rule that where common law and equity conflict, equity prevails. Many common law countries inherited this combined system.

For much of the twentieth century, the highest court in the United Kingdom could not overrule itself. In the 1898 case London Tramways v London County Council, the House of Lords declared that it was bound by its own earlier decisions, on the grounds that certainty mattered more than correcting occasional mistakes. Only Parliament could change a rule the Lords had laid down. That changed in 1966, when the Lord Chancellor issued a Practice Statement announcing that the Lords would treat their former decisions as normally binding but would depart from them when it appeared right to do so.

The power has been used sparingly, but one example shows its value. In Anderton v Ryan in 1985, the Lords held that a woman could not be guilty of attempting to handle stolen goods when it could not be shown that the goods were actually stolen. About a year later, in R v Shivpuri, they admitted that this reading of the Criminal Attempts Act 1981 had been wrong and overruled it. The United States Supreme Court has always been freer to reverse itself, most famously in Brown v Board of Education in 1954, which rejected the separate but equal doctrine accepted in Plessy v Ferguson in 1896.

Precedent only works if lawyers can find it, so common law systems developed a compact way of labelling cases. Take Donoghue v Stevenson [1932] AC 562. The names are the parties, usually with the one bringing the case or the appeal listed first. English criminal cases are brought in the name of the Crown, so they appear as R v Smith, where R stands for Rex or Regina, Latin for king or queen. Square brackets around the year show that the year is needed to find the right volume, AC refers to the Appeal Cases series of the official Law Reports, and 562 is the first page of the report.

Recording decisions has a long history. The medieval Year Books, kept from the late thirteenth century into the sixteenth, noted the arguments made in court, mostly for practising lawyers. Later reports were compiled privately by individual lawyers and cited by their names, and their accuracy varied a great deal. In 1865 the Incorporated Council of Law Reporting was set up to publish more reliable reports for England and Wales. Only a small share of cases are reported, chosen because they settle a point of law. Since 2001, English judgments have also carried neutral citations, which identify the court and a judgment number so a case can be found online.

Common law develops through binding judicial decisions rather than a single written code, it spread from England across much of the world, and it now operates alongside statute with courts shaping how legislation is applied.