328 U.S. 640 (1946)
One-Sentence Takeaway: Where the substantive offense is committed by one or more conspirators in furtherance of an unlawful activity, all members of the conspiracy are guilty of the substantive offense.
Summary: Defendant Daniel Pinkerton and his brother were charged with conspiracy to violate the tax laws and with two substantive tax violations. Although no evidence was introduced showing that Daniel participated directly in the commission of the substantive offenses, the district court instructed the jury that each brother could be found guilty of the other’s substantive offenses if they were both part of the same criminal conspiracy and “the acts referred to in the substantive counts were acts in furtherance of the unlawful conspiracy or object of the unlawful conspiracy.”
The United States Supreme Court upheld Daniel’s conviction under a theory of co-conspirator liability, but cautioned that the case would be different “if the substantive offense committed by one of the conspirators was not in fact done in furtherance of the conspiracy, did not fall within the scope of the unlawful project, or was merely a part of the ramifications of the plan which could not be reasonably foreseen as a necessary or natural consequence of the unlawful agreement.” Id. at 647-648.
Finally, the Court held that the defendants’ convictions for both conspiracy and the substantive crimes committed to further that conspiracy did not violate the Double Jeopardy Clause of the Fifth Amendment.