Common law is judge-made law. It dates back to the justiciars in England who travelled the countryside, meeting with the townspeople to solve disputes. They helped the king. In each community a local group of twelve senior men would tell the justiciars which persons were accused of breaching the local customary law. Those men or jurors would most often have no direct knowledge of the crime.
Once the accused was brought forward before the court, the jury would assist by telling exactly what the customary law was. The local accusers would tell their story. If the accused was found guilty, s/he might be put to a test such as a trial by ordeal.
Over time the same type of disputes arose and the justiciars started to apply the law in the same way in similar cases much like our judges today. This practice created the common law and the idea of precedents, that is, following the decisions in previous cases that had similar fact patterns. This information is provided in Handout 1: Common Law.