Before the Norman Conquest, different areas of England were governed by different systems of law, often adapted from those of the various invaders who had settled there; roughly speaking, Dane law applied in the north, Mercian law around the midlands, and Wessex law in the south and west. Each was based largely on local custom and, even within the larger areas, these customs, and hence the law, varied from place to place. The king had little control over the country as a whole, and there was no effective central government.
When William the Conqueror gained the English throne in 1066, he established a strong central government and began, among other things, to standardise the law. Representatives of the king were sent out to the countryside to check local administration, and were given the job of adjudicating in local disputes, according to local law. When these ‘itinerant justices’ returned to Westminister, they were able to discuss the various customs of different parts of the country and, by a process of sifting, reject unreasonable ones and accept those that seemed rational, to form a consistent body of rules.
During this process – which went on for around two centuries – the principle of stare decisis (‘let the decision stand’) grew up. Whenever a new problem of law came to be decided, the decision formed a rule to be followed in all similar cases, making the law more predictable. The result of all this was that by about 1250, a ‘common law’ had been produced, that ruled the whole country, would be applied consistently and could be used to predict what the courts might decide in a particular case. It contained many of what are now basic points of English law – the fact that murder is a crime, for example.
The principles behind this ‘common law’ are still used today in creating case law (which is in fact often known as common law). From the basic idea of stare decisis, hierarchy of precedent grew up, in line with the hierarchy of the modern court system, so that, in general, a judge must follow decisions made in courts which are higher up the hierarchy than his or her own ( the detailed rules on precedent are discussed later in this section). This process was made easier by the establishment of a regular system of publication of reports of cases in the higher courts.
The body of decisions made by the higher courts, which the lower ones must respect, is known as case law. The English common law system was exported around the world wherever British influence dominated during the colonial period. These countries, including the US and many Commonwealth countries, are described as having common law system. They are often contrasted with civil law system, which can be found in Continental Europe and countries over which European countries have had influence. The best-known civil law system is the French legal system, whose civil code has been highly influential.