---
title: "Conspiracy"
type: Legal Rule
source: https://casebriefly.com/legal-rules/conspiracy
---

# Conspiracy

Conspiracy is an agreement between two or more persons to commit an unlawful act, combined with the intent to achieve the criminal objective. Most modern jurisdictions also require an overt act in furtherance of the agreement.

## Definition

Conspiracy is an inchoate crime that criminalizes the agreement itself to commit an unlawful act. At common law, the crime was complete upon the formation of the agreement, requiring no further action. The Model Penal Code and most modern statutes add the requirement of an overt act in furtherance of the conspiracy, though the overt act need not itself be criminal -- even a minor preparatory step suffices.

The agreement need not be formal or express; it can be inferred from the conduct and circumstances of the parties. The prosecution must prove that each conspirator intended to agree and intended that the substantive crime be committed. Under the Pinkerton doctrine, each conspirator is vicariously liable for all foreseeable crimes committed by co-conspirators in furtherance of the conspiracy, even if the defendant did not participate in or know about those specific crimes.

A critical distinction exists between the common law bilateral approach and the MPC unilateral approach. Under the bilateral approach, at least two genuinely agreeing minds are required; if one party is an undercover officer or feigning agreement, no conspiracy exists. Under the MPC's unilateral approach, a defendant can be guilty of conspiracy even if the other party is an undercover agent, because the focus is on the defendant's own culpability. Conspiracy does not merge with the completed substantive offense, meaning a defendant can be convicted of both conspiracy and the target crime. Withdrawal can terminate liability for future crimes of co-conspirators but does not eliminate liability for the conspiracy itself at common law.

## Elements

- An agreement between two or more persons (bilateral) or by the defendant (unilateral under MPC)
- Intent to enter into the agreement
- Intent to achieve the unlawful objective of the conspiracy
- An overt act in furtherance of the conspiracy (required by MPC and most modern statutes, not at common law)
- The agreement need not be formal; it can be implied from conduct

## Key Case

Pinkerton v. United States, 328 U.S. 640 (1946)

## Landmark Cases

| Name | Citation | Significance |
| --- | --- | --- |
| Pinkerton v. United States | 328 U.S. 640 (1946) | Established that each conspirator is liable for all foreseeable substantive crimes committed by co-conspirators in furtherance of the conspiracy |
| Iannelli v. United States | 420 U.S. 770 (1975) | Addressed Wharton's Rule, holding that conspiracy does not merge when the legislature intended cumulative punishment |
| Krulewitch v. United States | 336 U.S. 440 (1949) | Discussed the breadth of conspiracy liability and its potential for prosecutorial overreach |
| Gebardi v. United States | 287 U.S. 112 (1932) | Held that a person protected by a statute cannot be convicted of conspiring to violate it |

## Exam Tips

- Distinguish between bilateral (common law) and unilateral (MPC) conspiracy when one party is an undercover agent
- Apply Pinkerton liability: ask whether the co-conspirator's additional crime was foreseeable and in furtherance of the conspiracy
- Remember that conspiracy does not merge with the target crime; a defendant can be convicted of both
- Check for Wharton's Rule when the target crime inherently requires multiple participants (e.g., dueling, adultery)

## Common Mistakes

- Assuming withdrawal eliminates conspiracy liability; withdrawal only cuts off liability for future substantive crimes, not for the conspiracy itself (unless the defendant thwarts the conspiracy under MPC)
- Forgetting that under the bilateral approach, if one conspirator is a government agent, there is no conspiracy because there was no genuine agreement
- Confusing conspiracy with accomplice liability; conspiracy punishes the agreement, while accomplice liability punishes aiding or encouraging the substantive crime

## Mnemonic Or Memory Aid

"A-I-O" -- Agreement, Intent, Overt act: the three requirements for modern conspiracy

## Related Rules

- accomplice-liability
- attempt
- solicitation
- felony-murder-rule

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Source: [Conspiracy — CaseBriefly](https://casebriefly.com/legal-rules/conspiracy)