A conspirator is a participant in a conspiracy. Conspiracy is a separate offense, by which someone conspires or agrees with someone else to do something which, if actually carried out, would amount to another federal crime or offense. It is an agreement or a kind of partnership for criminal purposes in which each member becomes the agent or partner of every other member. It is not necessary to prove that the criminal plan actually was accomplished or that the conspirator was involved in all stages of the plannig or knew all of the details involved.
The main elements that need to be proven are a voluntary agreement to participate and some overt act by one of the conspirators in furtherance of the criminal plan. If a person has an understanding of the unlawful nature of a plan and knowingly and willfully joins in that plan on one occasion, that is sufficient to convict him for conspiracy even though he had not participated before and even though he played only a minor part. A conspiracy may exist when the parties use legal means to accomplish an illegal result, or to use illegal means to achieve something that in itself is lawful. It is not necessary for guilt that the act be fully consummated. A statement of a conspirator in furtherance of the conspiracy is admissible against all conspirators, even if the statement includes damaging references to another conspirator, and often even if it violates the rules against hearsay evidence. Any conspirator is guilty of any substantive crime committed by any other conspirator in furtherance of the enterprise.