The chief justice is the presiding member of a supreme court in any of many countries with a justice system based on English common law, such as the High Court of Australia, the Supreme Court of Canada, the Court of Final Appeal of Hong Kong, the Supreme Court of India, the Supreme Court of Ireland, the Supreme Court of Japan, the Supreme Court of Nepal, the Supreme Court of New Zealand, the Supreme Court of Nigeria, the Supreme Court of Pakistan, the Supreme Court of the Philippines, the Supreme Court of Singapore, the Constitutional Court of South Africa, the Supreme Court of the United States, and provincial or state supreme courts/high courts.
The situation is slightly different in the three legal jurisdictions within the United Kingdom. The courts of England and Wales are headed by the Lord Chief Justice of England and Wales; in Northern Ireland's courts, the equivalent position is the Lord Chief Justice of Northern Ireland, and in the courts of Scotland the head of the judiciary of Scotland is the Lord President of the Court of Session, who is also Lord Justice General of Scotland. These three judges are not, though, part of the Supreme Court of the United Kingdom, which operates across all three jurisdictions and is headed by the President of the Supreme Court of the United Kingdom.
The chief justice can be selected in many ways, but, in many nations, the position is given to the most senior justice of the court, while, in the United States, it is often the President's most important political nomination, subject to approval by the United States Senate. Although the title of this top American jurist is, by statute, Chief Justice of the United States, the term "Chief Justice of the Supreme Court" is often used unofficially.
In some courts, the chief justice has a different title, e.g. president of the supreme court. In other courts, the title of chief justice is used, but the court has a different name, e.g. the Supreme Court of Judicature in colonial (British) Ceylon, and the Supreme Court of Appeals of West Virginia (in the US state of West Virginia).
The Chief Justice's personal ruling is equal in weight to the rulings of any associate judges on the court.
In several countries, the chief justice is second in line to the office of president or governor general (or third in line, if there is a president or governor lieutenant governor general), should the incumbent die or resign. For example, if the Governor General of Canada is unable to perform his or her duties, the Chief Justice of Canada performs the duties of the governor general.
Apart from their intrinsic role in litigation, they may have additional responsibilities, such as swearing in high officers of state; for instance, the Chief Justice of the United States traditionally administers the oath of office at the inauguration ceremony of the President of the United States, as does the Chief Justice of South Africa at the inauguration of the President of South Africa. In some countries, such as the United States, the Chief Justice is also responsible for presiding over certain legislative matters, such as during the impeachment trial of a president.