Court proceedings in countries that have a common law system (such as the UK, USA and Australia) are adversarial in nature.
This means that each party to the case presents argument and evidence in support of his or her version of events to the court, and the court decides whether the party that commenced proceedings has proved their version of events to the relevant standard (see Standard of proof in the Types of disputes section).
The court can only make decisions on the issues that the parties indicate to the court are in dispute, and decides only on the basis of the evidence and argument presented to the court by the parties. The court does not conduct its own investigation, or construct its own version of events.
In the majority of cases a judge or magistrate alone will hear the evidence and make the decision in a case. They are also responsible for imposing sentences in criminal cases. In some cases, superior courts may sit with more than one judge (for example the High Court or Federal Court sitting as a Full Court). Juries are used for serious (‘indictable’) criminal cases, and for some civil and coronial cases (see Juries).
The adversarial system may be contrasted with the inquisitorial system used in many European countries. In the inquisitorial system, the judge has a much more active role in directing the case and often makes inquiries, calls and examines witnesses and generally determines the matters that the court will decide.