Dr. William Hurwitz (defendant) prescribed very high doses of opioids to manage his patients’ pain. Many of his patients sold the drugs Hurwitz prescribed to them. Hurwitz claimed that the high doses were not improper but were necessary for proper pain management, particularly for patients who had become tolerant to lower doses. The United States (plaintiff) charged Hurwitz with drug trafficking and other crimes under the Controlled Substances Act, 21 U.S.C. § 841, for his prescription practices. The district court instructed the jury that it could not consider Hurwitz’s good faith in its analysis of the drug trafficking charge. The jury convicted Hurwitz, and he appealed, arguing that the district court’s jury instructions were improper.