Last Updated 1 August 2016

Common law is a collection of court decisions developed over hundreds of years by Australian superior courts, English courts and the courts of other countries that have similar legal systems to those of Australia and England. Of course, in Australia, decisions of superior Australian courts will be of more importance to our law than other countries’ decisions, but other countries’ decisions can be considered where relevant. Whenever courts have to consider cases involving either the interpretation of laws made by parliaments or cases where no laws exist, the effect is that by making a decision (and providing reasons for that decision), those courts are creating new laws. This adds to the body of law known as common law.

Particularly interesting or significant court judgments are reported case by case and collected into a variety of books known as law reports. Not all cases heard by courts in Australia will be reported—decisions of minor courts (like the Magistrates Courts in Queensland) are not recorded in law reports. In addition, cases in some superior courts are usually only recorded in law reports when they involve significant decisions that either create new common law or develop the common law previously made by judges.

Nowadays most decisions or cases, including unreported cases, are available online.

Judges deciding cases refer to the common law to guide them in making decisions about the particular case they are dealing with. This ensures that cases of a similar nature (e.g. with similar facts or similar questions of law) are decided using the same principles as previous similar cases.

The doctrine of precedent

Courts have developed a number of rules to guide them in their application of the common law. This body of rules is known as the doctrine of precedent and some are mentioned below:

    • A court, when it makes a decision, will usually give a reason or reasons for its decision, which will be based on the particular facts of the case. The principle of a case is sometimes referred to as the ratio decidendi (the reasoning for the decision). Judges are usually bound to decide a particular question in the same way that earlier cases with similar facts have been decided (i.e. judges are usually bound to apply the ratio decidendi of previous cases).


    • If the facts and the principles of the earlier cases are not exactly the same as those in a new case, a judge can still compare the situations and apply a common principle or develop a new, reasonably similar principle for the new facts.


    • Earlier cases with similar but not identical facts can be distinguished (i.e. the earlier case can be said to have been decided on different facts and, therefore, the judge or magistrate does not have to follow it).


    • Generally, a court must follow decisions that have been made by higher courts (e.g. a Magistrates Court must follow the decisions or reasoning of the Queensland District Court). Most courts are not bound to follow their own previous decisions. The High Court, for example, is not bound to follow the principles it has made in its own previous decisions (for the hierarchy of courts see The Court System chapter).


    • Higher courts do not have to follow the decisions of lower courts (e.g. the Queensland Supreme Court is not bound to follow decisions made by the Queensland District Court).


    • Where a court must follow the decision of another court, the decision is said to have binding authority (i.e. the court must follow the principle of the previous decision unless that decision can be distinguished as having been decided on different facts).


    • Courts outside Australia, such as the House of Lords in England and the Supreme Court of the United States, are outside the hierarchy of Australian courts. Decisions of foreign courts such as these are not binding on Australian courts, although their decisions may assist or guide Australian courts when they are about to make a decision on a new set of facts.


    • Where courts are not bound by previous decisions but still look to those decisions for guidance, the previous decision is said to have persuasive authority (i.e. the court can look at the previous decision to see whether it can be persuaded to follow it).


    • A judge’s decision on a case is binding on the parties to that case, unless one party successfully appeals against it.


    • Once the time for appeal has expired and neither party has appealed, the matter is settled and the case cannot be re-opened, except in extremely rare circumstances. The reason for this is that a case must have some finality, and parties and society need to have certainty about their legal rights and obligations that arise from that decision.


    • In very limited circumstances, a party can appeal a decision on special grounds even though the appeal time period has expired.


    • If a party appeals to a higher court within the time limit, the higher court can affirm (confirm) or overrule (change) the lower court’s decision. They may also remit the matter back to the lower court for retrial.


  • The decision of the highest court is final. The highest appeal court in Australia is the High Court of Australia.