The main issue arose from the fact that there was no evidence to show that Daniel Pinkerton participated directly in the commission of the substantive offenses, although there was evidence showing that these substantive offenses were committed by Walter Pinkerton in furtherance of the unlawful agreement or conspiracy existing between the brothers.
Daniel Pinkerton was not indicted as an aider or abettor, nor was his case submitted to the jury on that theory.
The criminal intent to do an illegal act by one of the conspirators in furtherance of the unlawful project is established by the formation of the conspiracy.
The Supreme Court noted that a different result would arise if the substantive offense committed by one of the conspirators was not 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 that could not be reasonably foreseen as a necessary or natural consequence of the unlawful agreement.
The Pinkerton liability rule does service where the conspiracy is one to commit offenses of the character described in the substantive charges.