Conspiracy. A combination or confederacy between two or more persons formed for the purpose of committing, by their joint efforts, some unlawful or criminal act, or some act which is lawful in itself, but becomes unlawful when done by the concerted action of the conspirators, or for the purpose of using criminal or unlawful means to the commission of an act not in itself unlawful.

A person is guilty of conspiracy with another person or persons to commit a crime if with the purpose of promoting or facilitating its commission he: (a) agrees with such other person or persons that they or one or more of them will engage in conduct which constitutes such crime or an attempt or solicitation to commit such crime; or (b) agrees to aid such other person or persons in the planning or commission of such crime or of an attempt or solicitation to commit such crime. Model Penal Code, § 5.03.

Crime of conspiracy is distinct from the crime contemplated by the conspiracy (target crime), Corn. v. Dyer, 243 Mass. 472, 509, 138 N.E. 296, 314, cert. denied, 262 U.S. 751, 43 S.Ct. 700, 67 L.Ed. 1214. Some jurisdictions do not require an overt act as an element of the crime, e.g. Corn. v. Harris, 232 Mass. 588, 122 N.E. 749.

A conspiracy may be a continuing one; actors may drop out, and others drop in; the details of operation may change from time to time; the members need not know each other or the part played by others; a member need not know all the details of the plan or the operations; he must, however, know the purpose of the conspiracy and agree to become a party to a plan to effectuate that purpose. Craig v. U. S., C.C.A.Cal., 81 F.2d 816, 822.

There are a number of federal statutes prohibiting specific types of conspiracy. See, eg., 18 U.S.C.A.  371. See also Chain conspiracy; Co-conspirator's rule; Combination in restraint of trade; Confederacy; Seditious conspiracy; Wharton Rule.

Chain conspiracy. Such conspiracy is characterized by different activities carried on with same subject of conspiracy in chain-like manner that each conspirator in chain-like manner performs a separate function which serves in the accomplishment of the overall conspiracy. Bolden v. State, 44 Md.App. 643, 410 A.2d 1085, 1091.

Civil conspiracy. The essence of a "civil conspiracy" is a concert or combination to defraud or cause other injury to person or property, which results in damage to the person or property of plaintiff. See also Civil conspiracy.

Overthrow of government. See Sedition.

Seditions conspiracy. See Sedition.

Conspiracy in restraint of trade. Term which describes all forms of illegal agreements such as boycotts, price fixing, etc., which have as their object interference with free flow of commerce and trade. See Antitrust acts; Clayton Act; Sherman Antitrust Act.

Conspirators. Persons partaking in conspiracy. See Conspiracy.

Conspire. To engage in conspiracy. Term carries with it the idea of agreement, concurrence and combination, and hence is inapplicable to a single person or thing, and one cannot agree or conspire with another who does not agree or conspire with him. See Conspiracy.