Dorothy Clark Garber (defendant) had a rare antibody in her blood that was used in the manufacture of blood-group-typing serum. She began selling her blood plasma to pharmaceutical companies. Between 1970 and 1972, Garber sold her blood plasma to Biomedical Industries Inc. (Biomedical) and Associated Biologicals, Inc. (Associated). Biomedical paid Garber a weekly salary of $200, provided her with a car, and in 1972 gave her a $25,000 bonus. Biomedical treated the weekly payment to Garber as a salary, withholding taxes and giving her a yearly W-2. The rest of the payments from Biomedical, as well the payments from Associated, were not treated like income; no taxes were withheld, and no W-2 was provided. Biomedical gave Garber a Form 1099 for the nonweekly payments that stated that it was for Garber’s information only, and Associated gave Garber no information related to taxes. Garber attached the W-2 forms from Biomedical to her yearly income-tax returns and did not pay taxes on the rest of her plasma-related income. Garber was charged with knowingly submitting incorrect income-tax information on her tax returns for 1970, 1971, and 1972. At trial, the government (plaintiff) had a tax professor offer his expert opinion that the money Garber received for selling her blood plasma was taxable income, though the professor admitted that the case was the first of its kind. Garber offered the expert opinion of a certified public accountant who stated that he believed the money Garber received was not taxable income. The district court did not admit either of these testimonies into evidence but did allow another expert presented by the government to argue that Garber owed taxes on unspecified income. A jury found Garber guilty of knowingly misstating her income on her 1972 tax return in violation of 26 U.S.C.A § 7201. The district court held as a matter of law that the money Garber received was taxable income. Garber appealed, arguing that she did not willfully file her taxes incorrectly because she believed the money she was paid was not taxable income.