Peter Aaron (defendant) was a supervisor for an investment firm, E.L. Aaron & Company. Two salespersons who were supervised by Aaron made unfounded recommendations to investors regarding stock. The Securities and Exchange Commission (SEC) (plaintiff) alleged that Aaron had failed to stop the fraudulent behavior of the salespersons even after becoming aware of the salespersons’ behavior. The district court found that Aaron had knowingly aided and abetted the salespersons’ fraud. On Aaron’s appeal, the court of appeals found that the issue of intent was not necessary, holding that § 17(a) of the Securities Act of 1933, 15 U.S.C. § 77q(a), required only a showing of negligence without the need for a showing of intent. The SEC appealed to the United States Supreme Court.