Nicole Tipton and Sadik Seferi owned and operated a restaurant in Iowa. Acting on a tip from the local police, agents of Immigration and Customs Enforcement executed search warrants at the restaurant and at an apartment where some restaurant workers lived. The agents discovered six undocumented aliens working at the restaurant and living together. When the I-9 forms for the restaurant’s employees were reviewed, none were found for the six aliens. They were paid in cash while other employees were paid by check. The jury found Tipton and Seferi guilty of hiring and harboring illegal aliens. Both were given prison terms. The defendants challenged the conviction, contending that they did not violate the law because they did not know that the workers were unauthorized aliens. Was that argument credible? Why or why not?