Not to be confused with formal proceedings of so-called Summary judgment (e.g. in United States courts, for civil matters where there is no dispute of material fact).

Summary Justice refers to the informal punishment of suspected offenders without recourse to a formal trial under the legal system.

• As procedure is a technical matter, requiring training, it is rarely any good in the practice of improvised justice, where emotions are often allowed to run high and cry out for swift and severe punishment (also improvised, whereas formal penal law generally prescribes measured punishment), without ample consideration, or even without due proof and rights of the defense.

Completely extra-legal 'justice' is called vigilante justice. The extreme, though the word is sometimes used by exaggeration for milder cases, is the Lynch mob which executes a suspect without having any legal authority to judge at all.

However, even the legal authorities themselves often have recourse, especially if the legal and political system are weak on checks and balances, to 'special courts', especially in regions and periods of increased insecurity, either in a controlled manner (emergency legislation, martial law - these are strictly speaking legitimate) or improvized, as often occurs in wartime or political power struggle (blurring the line between law and 'rebellious' crime).

• In some legal systems Summary Justice also refers to the system for trying and punishing offenders in a so-called court of Summary (or limited) Jurisdiction.

In England and Wales, for the purposes of jurisdiction, crimes are divided into 3 groups.

• Serious crimes must be heard in a Crown Court, tried before judge and a jury.
• Lesser, so-called Petty Crimes (punishable by a fine of no more than £5000 or up to a month's imprisonment), can be heard by two or more lay magistrates (or a legally qualified salaried stipendiary magistrate in urban areas) sitting without a jury. 95% of criminal cases in England and Wales are heard like this.
• The third group can be tried before either court. If a summary court thinks an offender deserves more punishment than it is allowed to exact, crimes in the third group can be referred to a Crown Court to pass sentence, but the Crown Court cannot hear any appeal against conviction.

Outside the pursuit of the legal order for the general good, the term is sometimes applied to punishments awarded by unauthorized persons or groups who feel it is a vital weapon to uphold a specific social order, such as solidarity amongst workers invoked to justify abuse (even beating) of strike breakers.