The term “kangaroo court” is a colorful piece of American slang used to describe an unfair trial which is conducted in clear contradiction of the legal establishment. It may be used in the sense of a trial convened by a self-appointed tribunal which quickly hands down harsh punishments, or in the sense of a clearly biased trial which had a predetermined outcome. Referring to a legal trial as a kangaroo court is a serious charge, since it implies that the trial was not conducted in a legal or fair fashion. Outside the United States, the term is not as widely heard.
There are several different explanations for the term, which originated in the United States, not Australia, the home of the kangaroo. The first is that a kangaroo jumps rapidly to conclusions, just as kangaroos jump quickly to move. The second suggests that the term is a wordplay on “claim jumpers,” the people who were most often charged in early kangaroo courts.
In either case, the term appears to have emerged in the early to mid-1800s, with the first written records of a kangaroo court appearing during the Gold Rush. These courts were often convened by miners and other people who had not received legal training, and they handed down sometimes unreasonably harsh punishments. The idea of quickie trials is also rather an old concept in the United States, thanks to the days of traveling judges in the American frontier. These judges were paid by the trial, so they had an impetus to quickly get through trials to earn more money.
Any type of sham legal proceeding can be very damaging. In most cases, a kangaroo court decides upon an already determined outcome, utterly depriving the defense of any chance to properly defend itself. In some instances, a kangaroo court may not even allow contradictory evidence or supporting materials for the defense, an action which is patently illegal. A kangaroo court may also be more subtle, depriving people of their rights in more insidious ways, such as through appointing an unfit lawyer, or by allowing a judge to remain on the stand despite being clearly biased.
The concept is related to a drumhead court-martial or drumhead trial, a sham court which is convened on the battlefield. In this case, a decision needs to be quickly made during the heat of battle so that soldiers and officers can carry on with their work. This decision is obviously colored by haste, and it may not be fair, accurate, or sensible. This term is derived from the idea of using the head of a drum for a writing surface, since no table is available.