A criminal conspiracy is generally a partnership formed to commit a crime or crimes. A criminal conspiracy exists when two or more persons form an agreement to violate a law that includes criminal penalties, and then take one or more steps designed to accomplish the goal of the conspiracy.

Federal and state statutes make criminal conspiracies illegal for two primary purposes: (1) to help combat the powerful forces created when two or more people collaborate to commit a crime; and (2) to allow criminal prosecutors (state and federal) to prosecute persons who play a role in planning a crime but who are not involved in the physical acts taken to complete the underlying crime.

For example, under federal law, if two or more persons conspire either to commit any offense against the United States, or to defraud the United States, or any agency of the United States in any manner or for any purpose, and one or more of such persons do any act to accomplish the objective of the conspiracy, each of the conspirators may be fined under and imprisoned for up to five years. See 18 U.S.C. §371. And most states have statutes (usually located in the penal or criminal code) that make criminal conspiracies a crime and include significant punishment upon conviction.

In Montana, criminal conspiracy is defined under Montana Code Annotated (MCA) 45-4-102. A criminal conspiracy occurs when two or more persons purposely agree to commit an offense and one of the parties commits an overt act in furtherance of the conspiracy. The agreement itself is the key element of the crime, and it is not necessary for the actual crime to be completed for a conspiracy charge to be valid. The punishment for conspiracy in Montana depends on the nature of the crime that the conspirators agreed to commit. If the intended crime is a felony, the punishment for conspiracy is typically set one classification lower than the punishment for the intended crime. This aligns with the dual purposes of conspiracy statutes: to dismantle the collaborative efforts to commit crimes and to prosecute those involved in the planning stages of criminal activities, even if they do not participate in the execution of the crime itself. At the federal level, as per 18 U.S.C. §371, individuals involved in a conspiracy to commit an offense against the United States or to defraud the United States can face fines and imprisonment for up to five years. An attorney can provide more specific guidance on how these laws might apply in a particular case.