Common Law Rule

Common Law Rule

The common-law baseline places the whole offense at the moment of agreement. A conspiracy became complete as soon as the parties reached an agreement with the requisite criminal intent, and the doctrine did not require any overt act in furtherance of that agreement.¹ Those two requirements correspond to the elements of the offense. The agreement is the actus reus, the physical element the prosecution must prove, and the intent to achieve the unlawful object is the mens rea, the required mental state.² Once the prosecution proves both, the offense exists, and nothing the conspirators do afterward is part of its proof. That answers the question the introduction left open: Okafor and Lindqvist, who agreed over coffee to commit a theft and then did nothing, committed conspiracy at the moment they agreed. The prosecution never has to show that either bought equipment, visited the site, or moved toward the theft in any other way.

The common law locates the crime in the agreement because an agreement is concrete in a way that a private intention is not. A design that rests in intention only is not indictable, but when two people commit themselves to carrying it out, the plot becomes an act in itself, each party's promise answering the other's. In Mulcahy v. The Queen, defendants charged with conspiring to foment the Irish rebellion argued that the indictment was defective because it alleged no overt act such as publishing writings or procuring arms, and the court rejected the argument, reasoning that "the very plot is an act in itself."³ The offense is therefore not a crime of pure thought, even though no step toward the object crime is required.

Two further reasons support punishing at this early point, and they work differently. The first concerns proof of intent. Preparatory conduct such as buying gasoline can be innocent or ambiguous, but a commitment between two minds to the same criminal end removes much of that doubt and makes it more likely that the crime will in fact be committed.⁴ The second concerns danger. Concerted action raises the odds that the object will be reached and lowers the odds that any participant will turn back, which is how the Supreme Court explained in Callanan v. United States why a group agreement threatens the public more than an individual's wrongdoing.⁵ Planning is also usually secret, so a rule that waited for a visible step would let the law intervene only after much of that danger had matured.

Completeness here refers to the elements of the offense, so a complete conspiracy may have accomplished nothing. A conspiracy stays complete when the plan fails, because the conspiracy and the crime that was its object are separate and distinct offenses. The failure of the object, or even an acquittal on the object crime, is therefore no bar to a conviction for the conspiracy.⁶ Poulterers' Case, a 1611 decision of the Court of Star Chamber, shows the rule near its origin. The defendants had banded together to bring a false accusation against Stone, but Stone was so clearly innocent that the grand jury refused to indict him, and the court still held that a conspiracy had occurred, because the gist of the offense is the agreement and the agreement is punishable even if its purpose is not achieved.⁷

Courtney and Anna supply an illustration of the same point from the other direction. They agreed to sell prescription drugs together, but Anna then excluded Courtney and the sale never took place, and Courtney can still be charged with conspiracy because the focus is the agreement, not whether both parties followed through or whether the crime was completed.⁸ What defeated the object differs between Poulterers' Case and Courtney's situation: the victim's obvious innocence in the first, a co-conspirator's decision to shut Courtney out in the second. That difference changes nothing, because in each situation the agreement and the intent already existed before the defeat occurred, and the offense attached at that earlier moment.

These twins mark the edge of the rule. The common-law rule removes only the overt act, and the agreement remains an element the prosecution must prove. The husband and the arsonist differ from the two acquaintances in one fact, whether the second person actually committed to the plan, and that fact carries the whole answer. Because everything the prosecution needs exists at the moment of agreement, the common law also allows no defense of abandonment: no later act can exonerate the actors, who, as in attempt, cannot go back once they have crossed the threshold of criminality.⁹ Later in this chapter, the treatment of duration and abandonment takes up how the Model Penal Code handles a change of heart. This baseline is not universal, however, since American conspiracy statutes have typically added an overt-act requirement, and the next section turns to those statutes.¹⁰