If two or more persons conspire … to commit any offense against the United States, or to defraud the United States, or any agency thereof … and one or more of such persons do any act to effect the object of the conspiracy, …

an offense against the United States has been committed.
A conspiracy has been characterized, rather than defined, as a partnership in criminal purposes, as a partnership in crime, and as a criminal partnership.
The unlawful combination being the gist of the conspiracy, it follows that there must be an agreement of some kind willingly entered into by the parties to it. There must be unity of design or purpose, a concert of will and endeavor, comprising what has been agreed to.
Mere knowledge or approval, without participation, does not make one a party to a conspiracy. Mere association does not establish a conspiracy, but there must be intentional participation in the transaction with a view to the furtherance of the common design and purpose.
A criminal conspiracy is an agreement or a mutual understanding knowingly made or knowingly entered into by at least two people to violate the law by some joint or common plan or course of action. A conspiracy is, in a very true sense, a partnership in crime.
A conspiracy or agreement to violate the law, like any other kind of agreement or understanding, need not be formal, written, or even expressed directly in every detail.
The government must prove that Defendant and at least one other person knowingly and deliberately arrived at an agreement or understanding that they, and perhaps others, would [violate some law(s)][defraud the United States] by means of some common plan or course of action as alleged in Count of the indictment. It is proof of this conscious understanding and deliberate agreement by the alleged members that should be central to your consideration of the charge of conspiracy.
[To prove the existence of a conspiracy or an illegal agreement, the government is not required to produce a written contract between the parties or even produce evidence of an express oral agreement spelling out all of the details of the understanding. To prove that a conspiracy existed, moreover, the government is not required to show that all of the people named in the indictment as members of the conspiracy were, in fact, parties to the agreement, or that all of the members of the alleged conspiracy were named or charged, or that all of the people whom the evidence shows were actually members of a conspiracy agreed to all of the means or methods set out in the indictment.]
Unless the government proves beyond a reasonable doubt that a conspiracy, as just explained, actually existed, then you must acquit Defendant .
Before the jury may find that Defendant , or any other person, became a member of the conspiracy charged in Count of the indictment, the evidence in the case must show beyond a reasonable doubt that Defendant knew the purpose or goal of the agreement or understanding and deliberately entered into the agreement intending, in some way, to accomplish the goal or purpose by this common plan or joint action.
[If the evidence establishes beyond a reasonable doubt that Defendant knowingly and deliberately entered into an agreement to [describe substantive offense] [defraud the United States], the fact that the defendant did not join the agreement at its beginning, or did not know all of the details of the agreement, or did not participate in each act of the agreement, or did not play a major role in accomplishing the unlawful goal is not important to your decision regarding membership in the conspiracy.]
Merely associating with others and discussing common goals, mere similarity of conduct between or among such persons, merely being present at the place where a crime takes place or is discussed, or even knowing about criminal conduct does not, of itself, make someone a member of the conspiracy or a conspirator
It is not necessary that a defendant be involved in a conspiracy from its inception or in every phase of the conspiracy in order to be criminally liable under Section 371.
The proof need not show that a defendant knew all of the details of the conspiracy or the identities of all participants.
A conspirator is liable for all acts and all declarations of co-conspirators made or done in furtherance of the conspiracy, including those occurring prior to his or her joining the conspiracy.
he term “overt act” means some type of outward, objective action performed by one of the parties to or one of the members of the agreement or conspiracy which evidences that agreement.
The government is not required to prove that the parties to or members of the alleged agreement or conspiracy were successful in achieving any or all of the objects of the agreement or conspiracy.
t is a defense to the charge of [conspiracy] [the substantive offense] in Count of the indictment that Defendant withdrew from the conspiracy before the commission of [any overt act] [the substantive offense] alleged in Count of the indictment.
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