From United States v. Johnston, , 2009 U.S. App. LEXIS 6981 (11th Cir. Mar. 30, 2009):

We also reject Johnston's argument that the experts improperly testified to legal conclusions. Although experts may not testify to legal conclusions, "testimony in the form of an opinion or inference otherwise admissible is not objectionable because it embraces an ultimate issue to be decided by the trier of fact." Fed. R. Evid. 704(a). Pinsley testified as to the appropriate standard of care in the medical field and gave her opinion that the prescriptions "were written without any legitimate medical purpose." Criminal knowledge and intent are issues of fact, not law. See United States v. Greenfield, 554 F.2d 179, 183 (5th Cir. 1977) ("[D]efendant strenuously asserted that the prescriptions ... were for a legitimate medical purpose and within the course of his professional practice. Necessarily, the issue of criminal intent or guilty knowledge was a factual issue for the jury to resolve."). Pinsley's testimony was therefore appropriate. In fact, Johnston questioned her own expert about whether he believed Johnston "acted in good faith in prescribing the substances" and "entered into ... a legitimate therapeutic physician/patient relationship" with each undercover officer.