The federal government (plaintiff) prosecuted Edward J. Brown (defendant) on illegal-drug and firearms charges. Brown filed Federal Rule of Criminal Procedure (Fed.R.Crim.P.) 12.2 notices that he intended to plead the affirmative defense of insanity and introduce expert testimony in support of that defense. Brown's psychologist, Dr. Fred Lindberg, was prepared to testify that Brown's post-traumatic stress disorder (PTSD) prevented Brown from making "correct choices" and conforming his conduct to the requirements of the law. The judge granted the government's motion in limine to exclude Lindberg's testimony from evidence, because it established no link between Brown's PTSD and the mens rea at issue. The judge invited Brown to proffer additional evidence to establish that link, but Brown could or would not do so. Brown then pleaded guilty to the charges, on condition that he be allowed to appeal the judge's ruling on the motion in limine. The judge agreed, and Brown appealed to the Tenth Circuit Court of Appeals.