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 Illinois, criminal conspiracy is defined under 720 ILCS 5/8-2 of the Illinois Compiled Statutes. A criminal conspiracy occurs when two or more people agree to commit a crime, and at least one of them performs an act in furtherance of that agreement. The state of Illinois recognizes the seriousness of collaborative efforts to commit crimes and provides legal mechanisms for prosecutors to charge individuals involved in the planning stages of criminal activity, even if they do not participate in the execution of the crime itself. The penalties for conspiracy in Illinois vary depending on the nature of the crime that was the object of the conspiracy, with potential sentences ranging from probation to imprisonment. Federal law, specifically 18 U.S.C. § 371, also addresses criminal conspiracy, allowing for the prosecution of individuals who conspire to commit any offense against the United States or to defraud the United States or its agencies. Under federal law, those found guilty of conspiracy can face fines and imprisonment for up to five years. Both state and federal statutes are designed to disrupt and penalize the collaborative efforts to commit crimes, reflecting the dual aims of preventing the formation of criminal partnerships and enabling the prosecution of those involved in the planning of criminal acts.