Kangaroo court

Kangaroo court is an informal pejorative term for a court that ignores recognized standards of law or justice, carries little or no official standing in the territory within which it resides, and is typically convened ad hoc. A kangaroo court may ignore due process and come to a predetermined conclusion. The term is also used for a court held by a legitimate judicial authority, but which intentionally disregards the court's legal or ethical obligations (compare show trial).
A kangaroo court could also develop when the structure and operation of the forum result in an inferior brand of adjudication. A common example of this is when institutional disputants ("repeat players") have excessive and unfair structural advantages over individual disputants ("one-shot players").
The term is known to have been used in the United States in 1841: an article in The Daily Picayune, New Orleans quotes the Concordia Intelligencer reporting several lynchings "upon various charges instituted by the Kangaroo court", asking "Don't comprehend: What is a Kangaroo court?" The term is not attested to have been used in Australia, native land of the kangaroo, or elsewhere before then.
The term kangaroo court may have originated in Britain. In the late 1700s, British courts began sentencing people convicted of various crimes to penal transportation to Australia. In the 1800s, this was sometimes referred to as the "Kangaroo Jump". It's possible that those sentenced to transportation may have protested that they had been convicted and sentenced by a kangaroo court. Some sources suggest that the term may have been popularized during the California Gold Rush of 1849 to which many thousands of Australians flocked. In consequence of the Australian miners' presence, it may have come about as a description of the hastily carried-out proceedings used to deal with the issue of claim-jumping miners. The derivation of the term is not known, although there has been speculation. It could be from the notion of justice proceeding "by leaps", like a kangaroo – in other words, "jumping over" (intentionally ignoring) evidence that would be in favour of the defendant. An alternative suggestion is that, as these courts are often convened quickly to deal with an immediate issue, they are called kangaroo courts since they have "jumped up" out of nowhere, like a kangaroo. Another possibility is that the phrase could refer to the pouch of a kangaroo, meaning the court is in someone's pocket.
Etymologist Philologos suggests that the term arose "because a place named Kangaroo sounded comical to its hearers, just as place names like Kalamazoo, and Booger Hole , and Okeefenokee Swamp, strike us as comical."
In 19th century America, an alternative term was “mustang” court, after horses that roamed the plains, thus evoking the image of a court presided over by a wild beast.
The term is still in common use in the Anglosphere.
The term is sometimes used without any negative connotation. For example, many Major League Baseball and Minor League Baseball teams have a kangaroo court to punish players for errors on the field, being late for a game or practice, not wearing proper attire to road games, or having a messy locker in the clubhouse. Fines are allotted, and at the end of the year, the money collected is given to charity or used for a team party at the end of the season.
A notable example includes in 2008, Mariano Rivera, then closer for the New York Yankees, was fined by his teammates after Rivera assisted division rival Roy Halladay in developing Halladay's cut fastball, Rivera's signature pitch.
Some examples of quasi-judicial proceedings that could be described as kangaroo courts are: