Second, law enforcement “drug profiling” testimony often state that it is “fair to say that a person driving [the drugs] from Point A to Point B … is going to be the person held responsible for the load,” which, as the Fifth Circuit noted, is the “functional equivalent” of the expert saying the driver knows they are carrying drugs.While Fifth Circuit precedent has held that, as a general rule, “a jury may infer that a defendant has knowledge of drugs in a vehicle when the defendant exercises control over the vehicle,” a law enforcement expert “may not offer an opinion or inference of the crime charged” under Federal Rule of Evidence 704(b) and 403; that this is an issue solely within the province of the “trier of fact.”Expert Cannot Testify as To Defendant’s KnowledgeIn effect, the appeals court has recognized that a law enforcement expert “may testify about the significance of certain conduct or methods of operation unique to the drug business so long as the testimony is helpful and its admission is not substantially outweighed by the possibility of unfair prejudice or confusion,” but the court has repeatedly cautioned prosecutors and instructed trial judges that “such testimony is not admissible if it amounts to the ‘functional equivalent’ of an opinion that the defendant knew he was carrying drugs.”This is generally referred to as “drug courier profile” or “drug profiling” evidence.

Today, the Supreme Court of the United States granted certiorari in one case:Diaz v. United States, No. 23-14: This criminal drug-trafficking case involves interpretation of Rule 704(b) of the Federal Rules of Evidence, which bars expert witnesses from stating “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.” The question presented is: In a prosecution for drug trafficking—where an element of the offense is that the defendant knew she was carrying illegal drugs—does Rule 704(b) permit a governmental expert witness to testify that most couriers know they are carrying drugs and that drug-trafficking organizations do not entrust large quantities of drugs to unknowing transporters?

The defendants argued that the experts’ opinions were inadmissible legal conclusions. Under Federal Rule of Evidence 704, opinions that merely tell the jury what result to reach or state a legal conclusion in a way that says nothing about the facts are objectionable because such opinions are not helpful to the trier of fact. Although Rule 704 abolished the “ultimate issue” rule that prohibited witnesses from offering opinions as to the ultimate issue to be adjudicated in a case, if the ultimate issue is embraced by an expert’s opinion it must be a factual one.The court reviewed the experts’ reports and concluded that those reports may contain inadmissible legal conclusions.

Whether a given trade dress is “presumptively valid” or “enforceable” are ultimately calls for the court to make, not for an expert witness. Similarly, whether a registration comports with USPTO requirements is also a legal conclusion and not appropriate for expert testimony.In walking a mile in Doc Martens’ shoes, we can see where it was possibly headed with this proffered testimony. Federal Rule of Evidence 704 tells us that “[a]n opinion is not objectionable just because it embraces an ultimate issue.” After all, whether a given trade dress is valid and enforceable is certainly one of the “ultimate issues” in any trade dress infringement case.

US v. Garcia-Martinez, 2018 WL 1767712 (10th Cir. April 12, 2018) (unpublished): In this drug case, the Tenth Circuit rejects defendant's arguments that the government violated Giglio and Brady by failing to disclose impeachment information regarding two confidential informants, and that the district court erred by allowing an expert witness to testify regarding his mental state in violation of FRE 704(b).

This provision does not apply to a defense based on the inability to form the specific intent to commit the crime. Psychiatric evidence of a defendant’s inability to form the specific intent is admissible and not barred by 18 U.S.C. §17(a), or Fed.R.Evid. 704(b) which prohibit a psychiatric expert testifying about the mental condition of a defendant with regard to the “ultimate issue” of the accused’s capacity to form the requisite intent.United States v. Samuels, 801 F.2d 1052 (8th Cir. 1986)The evidence in this case was insufficient to establish that the defendant was sane at the time that he wrote a letter to the President threatening to kill him.

U.S. v. Becknell, 2015 WL 874398 (3/3/15) (Kan.) (unpub'd) - The 10th holds it would be reversible error in violation of Federal Rule of Evidence 704(b) for an expert to testify that a defendant in a § 924(c)(1)(A) case possessed a firearm "in furtherance of" a crime. But in this case where, as the 10th described it, the officer expert "did everything but state that inference," there is no error.

Furthermore, courts have “broad discretion” respecting the admission of expert testimony. E.g., Smith v. Rodillo, 2014 WL 5859629 (Ga. App. Ct. 2014); Phelps-Roper v. Heineman, 2014 WL 5489365 (D. Neb. 2014). Experts may, therefore, express their views about an “ultimate issue” that must be resolved by the trier of fact. FRE 704(a). But they may not present a “legal conclusion” or “direct[] a jury as to the result it should reach in making a decision.”

Ultimate issue testimony The Sixth Circuit assumed that it was error for the district court to admit Gilson’s legal conclusion — the district court admitted as much. While opinion evidence is not automatically objectionable under Federal Rule of Evidence 704(a) when it embraces an ultimate issue, nonetheless, it must be helpful to the trier of fact. A lay witness’s opinion as to an ultimate issue will “seldom” meet this test because “the jury’s opinion is as good as the witness’[s].”

No error in admitting law enforcement expert witness for plaintiff sho testified that department's treatment of employee reflected retaliation for filing complaints of discrimination. Not a proper basis to exclude that expert testifies on"ultimate conclusion" as such testimony is sanctioned under FRE704 for lay testimony. Panel expresses doubt that his testimony assisted the jury, but any error was harmless in light of fact that jury made "painstakingly" exact findings on each of four defendants (finding liability only for one).