Definition
An agreement between two or more persons to accomplish an unlawful purpose, or to accomplish a lawful purpose by unlawful means. Conspiracy is both a crime and, in a distinct form, a civil wrong.
1. Criminal conspiracy. The offense is complete upon agreement, regardless of whether the underlying objective is ever carried out. Most modern jurisdictions also require at least one overt act by any conspirator in furtherance of the scheme — though the overt act need not be criminal in itself. Each conspirator is criminally liable for the acts of all co-conspirators committed in furtherance of the conspiracy, even if those acts were not personally performed or foreseen in detail.
2. Civil conspiracy. An actionable civil wrong in which two or more persons combine to accomplish an unlawful objective or a lawful objective through unlawful means, and by doing so cause actual harm to the plaintiff. Unlike criminal conspiracy, civil conspiracy requires proof of actual damages. The tort does not stand alone — it depends on the commission of an underlying wrongful act; the conspiracy itself is the mechanism of liability, not an independent cause of action.
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Common Language
Modern common usage (Wiktionary): A secret plan made by two or more people to do something that is harmful or illegal; loosely, any secret or hidden plot.
Historical common usage (Webster's 1913): "A combination of men for an evil purpose; an agreement between two or more persons to commit a crime in concert; a plot."
The common meaning of conspiracy — a secretive scheme — tracks the legal meaning closely enough that lay readers feel confident they understand the term. That confidence is misleading in two directions. First, in criminal law the agreement itself is the crime; secrecy is not an element and the object need not involve violence or dramatic plotting. Two people openly agreeing to commit a minor fraud qualify. Second, civil conspiracy and criminal conspiracy are analytically separate creatures with different elements, different parties who may bring the claim, and different remedies. The single common word papers over that division.
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Common Confusion
Conspiracy vs. Attempt. Both are inchoate offenses, but they are distinct. Attempt requires substantial steps toward a crime and focuses on individual conduct. Conspiracy focuses on the agreement between persons and does not require any steps toward execution beyond (where required) a minimal overt act. A person can be charged with both conspiracy and attempt to commit the same underlying offense.
Conspiracy vs. Aiding and Abetting. Conspiracy requires a prior agreement. Aiding and abetting attaches liability to one who assists a crime already in progress without necessarily having agreed in advance. The distinction matters in historical sources, which sometimes use "confederacy" or "combination" for what modern law calls conspiracy, and "accessory before the fact" for conduct that might today be charged as conspiracy, aiding and abetting, or both.
Criminal vs. Civil Conspiracy. The shared label obscures a substantial doctrinal gap. Criminal conspiracy can be prosecuted without any completed harm to a victim; the agreement (and overt act where required) is enough. Civil conspiracy requires actual damage caused by the underlying wrongful act. Researchers moving between criminal and civil sources should not assume authorities on one form of the doctrine apply to the other.
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Core Elements
Criminal Conspiracy (majority rule):
1. Agreement — a mutual understanding between two or more persons
2. Intent to agree and intent to accomplish the object of the agreement
3. An unlawful objective (or a lawful objective pursued by unlawful means)
4. An overt act in furtherance of the conspiracy (required in most, but not all, jurisdictions and by federal statute for most offenses)
Civil Conspiracy:
1. A combination of two or more persons
2. A common design to accomplish an unlawful purpose or a lawful purpose by unlawful means
3. An overt act in furtherance of the common design
4. Actual damage to the plaintiff resulting from the acts committed pursuant to the conspiracy
Note on the "two or more persons" requirement: The traditional rule required at least two guilty minds — a single defendant could not conspire with an undercover officer, an innocent dupe, or a legal fiction such as a corporation acting through its own agents. Modern federal law and many state statutes adopt a unilateral approach, under which one person's agreement is sufficient even if the other party feigns agreement or is legally incapable of conspiring.
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Recognized Forms
/ SUBTYPES
Wheel conspiracy: A single hub defendant makes separate agreements with multiple spoke defendants who have no agreement with each other. Whether the spokes constitute a single conspiracy or multiple separate conspiracies is a recurring evidentiary and variance issue.
Chain conspiracy: Sequential actors each handle one stage of a common criminal enterprise (classic in drug distribution cases), with each link connected to the next. The question is whether all participants share sufficient knowledge of the overall scheme to be bound together in one conspiracy.
Drug conspiracy: Governed by specific federal and state statutes that modify standard conspiracy doctrine in important ways — particularly regarding sentencing, the treatment of drug quantity, and the scope of co-conspirator liability. Treated as a distinct research area in the Law Mind corpus.
RICO conspiracy: A statutory form under 18 U.S.C. § 1962(d) requiring agreement to participate in a pattern of racketeering activity. Operates under its own case law and should not be researched interchangeably with common law conspiracy doctrine.
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Why It Matters in Research
The single most important navigational point: criminal conspiracy doctrine and civil conspiracy doctrine share a name and a general structure but have evolved largely independently. Sources that analyze one do not reliably illuminate the other. Before using any authority, confirm which form is being addressed.
Historical sources present significant traps. Rapalje & Lawrence and contemporaneous treatise writers use "confederation" and "combination" interchangeably with conspiracy, and they describe the law at a moment before the overt act requirement was uniformly adopted and before the bilateral/unilateral split in conspiracy theory emerged. Conclusions drawn from those sources about what constitutes a completed conspiracy, or whether a single defendant can conspire alone, may be historically interesting but are not reliable statements of current majority doctrine.
The scope of co-conspirator liability — under which each member of a conspiracy is liable for the foreseeable acts of all other members — makes conspiracy charges exceptionally broad. Researchers analyzing criminal exposure, civil damages, or evidentiary questions (particularly the co-conspirator exception to the hearsay rule) should trace these issues separately; they arise in different doctrinal contexts and generate different bodies of authority.
Overt act variation is a research trap in multi-jurisdictional matters. Federal law requires an overt act for most (but not all) conspiracy offenses — notably, drug trafficking conspiracies under 21 U.S.C. § 846 do not require one. State law varies further. The absence of an overt act requirement does not mean the law is older or more permissive in every respect; it may reflect a legislative choice to treat the agreement itself as sufficiently dangerous.
In drug conspiracy research specifically, quantity attribution and sentencing exposure for individual defendants within a larger conspiracy is a heavily litigated area that has produced its own line of authority distinct from general conspiracy doctrine. Use the dedicated drug conspiracy encyclopedia entry as the entry point for that research.
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Historical Dictionary Support
Rapalje & Lawrence (1883) define conspiracy as "a combination or confederacy between two or more persons formed for the purpose of doing, by their combined action, some unlawful act, or some act which though not unlawful in itself, becomes so by the concerted action of the conspirators, or some act which is unlawful in the means by which it is to be attained." The definition is sound as a historical baseline and its core structure — agreement, two or more persons, unlawful objective or unlawful means — survives in modern doctrine.
What the Rapalje & Lawrence treatment does not capture, because the questions had not yet been resolved at time of writing: the systematic development of overt act doctrine, the emergence of the bilateral/unilateral split, the constitutional limitations on co-conspirator liability, or the later distinction between wheel and chain conspiracy structures. Their treatment of civil conspiracy is underdeveloped relative to what the tort has become, particularly regarding the requirement of an independent underlying wrong.
The 1883 definition's emphasis on "combined action" reflects the bilateral model that dominated common law thinking and persisted well into the twentieth century. Researchers using Rapalje & Lawrence to interpret pre-twentieth century materials will find the definition accurate for its period; researchers attempting to apply it to modern doctrine should treat it as a starting point and not a conclusion.
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Jurisdictional Note
Federal law and most states require an overt act for criminal conspiracy, but a significant minority do not, and federal drug trafficking conspiracy statutes expressly dispense with the requirement. The bilateral/unilateral split similarly divides jurisdictions: the Model Penal Code adopts the unilateral approach, but a number of states retain the bilateral rule. Civil conspiracy doctrine varies considerably in whether courts treat it as an independent tort or purely as a theory of vicarious liability for an underlying wrong.
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Encyclopedia Cross-Reference
The Law Mind Criminal Law Encyclopedia — Inchoate Crimes: Conspiracy (Agreement and Overt Act): Primary reference for criminal conspiracy doctrine, elements, and the overt act requirement.
The Law Mind Criminal Law Encyclopedia — Drug Conspiracy: Essential for federal and state drug conspiracy charges, quantity attribution, and sentencing exposure within a conspiracy.
The Law Mind Torts & Personal Injury Encyclopedia — Intentional Torts: Civil Conspiracy: Primary reference for the civil tort, its elements, the underlying-wrong requirement, and damages.
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