operator stands with arms and looks forwardU.S. District Judge James I. Cohn recently heard arguments on a defendants’ motion to exclude the testimony of a plaintiffs’ military analyst with expertise in investigating and analyzing military structures in the context of violence against civilians during armed conflict.

This military expert had nearly two decades of experience investigating international criminal law and human rights violations, including 14 years as an analyst and investigator for the International Criminal Tribunal for the former Yugoslavia.

Plaintiffs sought to have its expert give an opinion on whether the Defendants in these cases—the former President of Bolivia and the former Minister of Defense of Bolivia were responsible, under the doctrine of command responsibility, for the allegedly improper use of force by the Bolivian Armed Forces against Bolivian civilians, including the eight decedents in these cases.

Plaintiff’s military expert opined on three areas: (1) command responsibility and the de jure and de facto roles of Defendants during the events at issue in these cases; (2) the military as an institution in Bolivia; and (3) an evaluation of the Bolivian military’s violence against civilians in 2003, namely, whether there was a deliberate pattern of military violence and, if so, whether that violence was justified.

Defendants contended that Plaintiff’s military expert wasn’t qualified to opine on the structure of the Bolivian military and Defendants’ roles within that structure. They also claimed that Plaintiff’s military expert’s opinions were unreliable because they were based on the opinions of another of Plaintiffs’ proffered experts. And third, Defendants asserted that Plaintiff’s military expert did nothing more than offer legal conclusions in the guise of expert opinion.

Judge Cohn wrote in his opinion, quoting precedent, that an expert “may not testify to the legal implications of conduct or tell the jury what result to reach.” The district court “must be the jury’s only source of law, and questions of law are not subject to expert testimony.” Here, Defendants said that the military expert inappropriately interpreted and applied the command responsibility standard and did so in a way that was prejudicial and would confuse the jury.

The military expert’s report tracked the accepted three-pronged standard. The first three sections of his report analyze each element, with his fourth and final section addressing “possible defenses.” He ultimately concluded that each element was met, and that Defendants’ “possible defenses” all failed. Defendants contended that his opinions were nothing more than an impermissible legal conclusion regarding Defendants’ liability.

Judge Cohen found that the expert not only offered an opinion on the legal standard itself, but he then applied that standard and concluded that it had been met in these cases—which he can’t do. The judge explained that an expert may offer his opinion as to facts that, if found, would support a conclusion that the legal standard at issue was satisfied. However, he can’t testify as to whether the legal standard has been met. Expert testimony amounts to a legal conclusion if it either “track[s] the language of the applicable statute” or uses a term that “has a specialized legal meaning that is more precise than the lay understanding of the term.”

Plaintiffs described their military expert’s opinions as an exercise in explaining how certain facts concerning the Bolivian military’s structure and Defendants’ actions during 2003 supported a legal conclusion about command responsibility. The judge acknowledged that while the expert did analyze facts that, if found, would support a conclusion that the command responsibility standard was met. But he went one step further and made a legal conclusion.

As a result, the judge permitted the military expert to testify as to certain facts that, if found, would suggest a conclusion that Defendants failed to prevent or punish criminal conduct, but he was prohibited from offering an ultimate legal conclusion that Defendants failed to do so.

Defendants raised an additional reason for excluding Plaintiff’s military expert’s command responsibility opinions, claiming that the military expert erroneously imported the non-legal principles of “command and control” and “non-delegation of responsibility” into his analysis of the superior-subordinate element of the command responsibility doctrine. Defendants asserted that permitting him to testify on the issue would be prejudicial and confusing to the jury.

Exclusion of testimony under Rule 403 is appropriate, the judge wrote, “if the probative value of otherwise admissible evidence is substantially outweighed by its potential to confuse or mislead the jury.” The judge noted that Rule 403 is “an extraordinary remedy which the district court should invoke sparingly, and the balance should be struck in favor of admissibility.” Even assuming that Plaintiff’s military expert misinterpreted and misapplied the command responsibility doctrine as Defendants suggested, the judge found it inconsequential; any prejudice that may result didn’t substantially outweigh the probative value of the expert’s opinions on that issue.

The court ruled that the military expert couldn’t offer opinions about the specific circumstances of decedents’ deaths and couldn’t mention or reference Plaintiff’s other expert’s report or the opinions contained therein, including whether decedents were intentionally shot by the Bolivian military. Finally, while Plaintiff’s military expert was permitted to provide his command responsibility analysis, he was to offer no opinion on the ultimate legal question whether the elements of the command responsibility doctrine were satisfied in these cases.

Defendants’ motion was granted in part and denied in part.