Jermaine Eggleston v. United States

Federal Rule of Evidence 704(b) states, “[i]n a criminal case, an expert witness must not state an opinion about whether the defendant did or did not have a mental state or condition that constitutes an element of the crime charged or of a defense. Those matters are for the trier of fact alone. ” The question presented is whether the government may circumvent Federal Rule of Evidence 704(b) by eliciting an expert opinion on the mental state of a “hypothetical” person whose circumstances – including the receipt of a specific, unique text message – are a carbon copy of the defendant’s, thereby having the expert functionally opine on the defendant’s mental state.