In the 1915 case of Lamar v. United States, the Supreme Court ruled on a matter involving fraudulent use of the U.S. mail system. The defendant, Lamar, was accused of using mail to defraud investors through his company's sale and leaseback scheme for typewriters. He argued that he could not be prosecuted because his corporation was an entity separate from himself as an individual; therefore it should bear responsibility for any alleged fraud committed via its operations. The court rejected this argument stating that corporations are merely associations of individuals under law and those individuals can still be held accountable for their actions within corporate structures if they engage in illegal activities such as fraud. This decision established important legal precedent regarding corporate personhood and liability - affirming that while corporations may have certain rights and responsibilities under law, these do not absolve associated individuals from personal accountability when they commit crimes or other wrongful acts.

In the dissenting opinion for Lamar v. United States, Justice Oliver Wendell Holmes Jr. argued that the majority's interpretation of the law was too narrow and failed to consider its broader implications. He believed that a person could be guilty of conspiracy even if they were not directly involved in carrying out an illegal act, as long as they had knowledge of it and intended to further it. In this case, he felt that Lamar should have been found guilty because he knowingly participated in a scheme designed to defraud banks through false representations about his financial status. The fact that some participants may not have known all details or understood their illegality did not absolve them from guilt according to Holmes' view on conspiracy law application.