The core federal drug statute is 21 U.S.C. § 841. This statute focuses exclusively on the manufacture, distribution, dispensation, or possession of a “controlled substance.” The statute has little, if any, interest in the personal use of narcotics. It is normally used in conjunction with prosecutions targeting organized drug trafficking operations, those involving two or more individuals who conspire to manufacture and distribute illicit drugs, such as heroin, cocaine, or methamphetamine. To secure a conviction under § 841(a), the government must prove, at a minimum, that there was a “knowing” and/or “intentional” drug trafficking violation.


Expert Testimony of Law Enforcement Agents


And this is where law enforcement enters the prosecutorial process. To prove the requisite knowing and intentional mens rea (mental state), federal prosecutors are often exclusively dependent upon the “expert” and lay testimony of members of law enforcement. Federal Rule of Evidence 702 allows testimony of a law enforcement officer who has “specialized knowledge” that may “assist the trier of fact” (jury or judge). This requires the trial court to make a specific finding that a law enforcement officer has sufficient “knowledge, skill, experience, [or] training” to qualify as an “expert witness.”


In his 2012 article in the George Mason Law Review titled “To Serve and Protect? Officers as Expert Witnesses in Federal Drug Prosecutions,” University of Arkansas Law School Professor Brian C. Gallini made this significant observation about the use of law enforcement agents in federal drug conspiracy trials:


“ … Relying on that standard, federal courts regularly admit members of law enforcement’s expert testimony on a variety of topics, including those relevant to federal drug prosecutions. Admitting members of law enforcement’s expert testimony under these circumstances have consequences, particularly in federal drug prosecutions. First, in the words of the federal evidentiary rules, juries may hear testimony that is not ‘the product of the reliable principles and methods.’ And, second, when courts routinely admit members of law enforcement’s expert testimony, they enable officers to testify without an empirical basis. For example, such officers may fail to testify about both the nature of the particular drug transactions and whether the defendant possessed the requisite mental state while participating in the transaction.”


Expert Testimony Can Cross the Line to Misconduct


The “consequences” of this carte blanche use of law enforcement’s expert testimony are numerous, recurring, and, as the Fifth Circuit recently noted in a July 25, 2018 decision, often cross the line from zealous prosecution into the corruptive influences of prosecutorial conduct. The Fifth Circuit has aggressively sought to limit these consequences in order to keep federal drug trials within the bounds of fairness and impartiality.


Ten years ago the Fifth Circuit in United States v. Vedia pointed out how expert law enforcement testimony can create intended and/or unintended consequences. First, the appeals court has found error when a law enforcement agent “made the generalization, albeit not quite directly, that drivers [of vehicles carrying drugs] know they are carrying drugs.” 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 Knowledge


In 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. This evidence comes into play in federal drug prosecutions when law enforcement expert witnesses seek to opine that a defendant’s “conduct” matches the “profile” of a drug courier and, therefore, they must have known they were transporting drugs. However, the federal evidentiary rules provide that prosecutors cannot use, and the trial court must not admit, this evidence “to prove substantive guilt based on similarities between defendants and a profile.”  Federal Rule of Evidence 704(b) expressly states that “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.”


Determining Mental State of Defendant is Jury’s Job


As Professor Gallini so succinctly pointed out:


“It is therefore uniquely within the trier-of-fact’s province to find, as a factual matter, whether defendant did or did not possess the mens rea associated with the crime charged. When a member of law enforcement takes the stand as an ‘expert’ and thereafter testifies that defendant’s activities are consistent with drug trafficking, the witness has unconstitutionally usurped the jury’s role.


“Drug-profiling testimony most clearly manifests this problem. When members of law enforcement testify as experts about drug-courier profiles, courts become concerned that the jury will rely on that testimony as substantive evidence of defendant’s guilt (because defendant’s activities might resemble the profile). Although discussed above in the context of Rule 702, courts have also noted potential problems with drug-courier-profile evidence in the context of Rule 704(b). Again, though, regardless of which Rule applies to the judiciary’s concern, the concern itself remains the same: a jury may accept that defendant is guilty simply because his behavior matches the profile described by a law enforcement member’s expert testimony.”


Drug Profile Testimony Must be Limited


Drug profile evidence may be beneficial to investigation and apprehension, but it cannot be used as federal prosecutors so often use it with the trial court’s benign approval in a federal drug prosecution to establish the defendant’s guilt. Since federal prosecutors do not always have an “actual connection” between the defendant and the drug trafficking offense charged, they utilize drug profiling evidence presented through law enforcement as a shortcut to conviction. This is a tempting trial tactic because, as the Fifth Circuit has noted, there is a “fine but critical line” that separates “testimony concerning methods of operation unique to the drug business” and “testimony comparing a defendant’s conduct to the generic profile of a drug courier.”


Defense Counsel Must Timely Object


The one common theme in many of the Fifth Circuit’s drug trafficking cases involving law enforcement expert testimony is the failure to defense counsel to timely object to improper drug profiling testimony by law enforcement agents, some of whom are actually involved in the investigation and apprehension of the defendant. While the trial court at the request of the prosecution may permit law enforcement expert testimony under Rule 702, it is the responsibility of defense counsel to not only challenge the admissibility of such testimony but their duty to timely object under Rules 704(b) and 403 to any improper drug profile testimony that invades the province of the trier of fact.


The trial court can only rule on a challenge that the drug profile testimony had crossed that “fine but critical line” between admissibility and inadmissibility if an objection is made—and the Fifth Circuit can only review the issue straightforwardly under its existing precedents if a timely objection was made at the trial level.


Government prosecutors should not cross that “fine but critical line” but they will, and the trial courts will generally let them get away with it unless defense counsel intercedes for his client.


Justice is not always recognized by prosecutors and it is not always administered by the federal courts. It must be relentlessly demanded by defense counsel.