Judicial independence is the concept that the judiciary should be independent from the other branches of government. That is, courts should not be subject to improper influence from the other branches of government or from private or partisan interests. Judicial independence is important to the idea of separation of powers.
Many countries deal with the idea of judicial independence through different means of judicial selection, or choosing judges. One way to promote judicial independence is by granting life tenure or long tenure for judges, which ideally frees them to decide cases and make rulings according to the rule of law and judicial discretion, even if those decisions are politically unpopular or opposed by powerful interests. This concept can be traced back to 18th-century England.
In some countries, the ability of the judiciary to check the legislature is enhanced by the power of judicial review. This power can be used, for example, by mandating certain action when the judiciary perceives that a branch of government is refusing to perform a constitutional duty or by declaring laws passed by the legislature unconstitutional.