Conspiracy, a crime special to common law jurisdictions and largely unknown, except in modest forms, in continental European countries, is one of the most controversial of all substantive crimes. It affords great advantages to law enforcement, since it avoids multiple trials, permits prosecution of preparatory activity at an early stage, facilitates prosecution against organized criminality, and extends a number of evidentiary and procedural advantages to the prosecution. At the same time, it constitutes what Justice Jackson in Krulewitch termed an "elastic, sprawling and pervasive offense" (445) that departs from traditional requirements of liability: (1) the crime of conspiracy is vaguely defined and its contours are often unpredictable; (2) it permits conviction on acts largely mental in character; (3) its essential feature, an agreement, is often diluted to something approaching suspicion of agreement; and (4) it affords a highly tenuous basis for holding the defendant for substantive crimes committed by others. Moreover, the procedural advantages to the prosecution impose corresponding disadvantages on the defendant, disadvantages thought inappropriate and unfair when other crimes are charged.
The balance has been struck on the side of retaining the offense with modest revisions, despite long-standing criticism ( Johnson). The crime of conspiracy will in all likelihood remain an integral part of the prosecutor's arsenal. Whether it will be kept within tolerable bounds depends on how sensitively and critically prosecutors employ it, courts administer and interpret it, and legislators act to preclude its excesses.