John Park (defendant) was president and chief operating officer of Acme Markets, Inc., (Acme) (defendant), a national retail food chain. The Government charged Acme and Park in federal district court with several violations of the Federal Food, Drug, and Cosmetic Act of 1938 (FDCA). The Government alleged that Park and Acme had received food at its warehouses that had been shipped in interstate commerce and allowed the food to be accessed by rodents and exposed to contamination. Acme pleaded guilty, but Park proceeded to trial. At trial, the prosecution produced evidence that the Food and Drug Administration (FDA) had sent Park a letter regarding the unsanitary conditions at Acme’s Philadelphia, Pennsylvania warehouse in April 1970. The following year, the FDA found similar conditions at Acme’s Baltimore, Maryland, warehouse. Another letter was sent to Park after the unfavorable inspection. In March 1972, another inspection of the Baltimore warehouse showed slight improvement, but still revealed evidence of rodent “activity” in the food. Park was the only defense witness and testified that he investigated the sanitary issues and had conferred with corporate officers regarding the matter. On cross-examination Park conceded that providing sanitary conditions for food offered for sale to the public was something that he was “responsible for in the entire operation of the company.” The jury found Park guilty and he appealed. The court of appeals reversed and held that the district court should have instructed the jury that the government had the burden of establishing “wrongful action” by Park. The U.S. Supreme Court granted certiorari to review.