Given that the Rules of Evidence were developed without regard to, or prior to the development of, principles of cognitive science, one might expect courts to use scientific research to mediate those rules and, especially, to inform the exercise of discretion.  But as two divergent lines of cases show, although each involves how a visual occurrence in the courtroom might impact jury decision-making, the turn to science is selective if not random.

Let us start with shackling criminal defendants.  This act has been condemned as a matter of constitutional law since 1970, in part because “it [is] possible that the sight of shackles and gags might have a significant effect on the jury’s feelings about the defendant…”  Illinois v. Allen, 397 U.S. 337, 344, 90 S. Ct. 1057, 1061 (U.S. 1970).  That tentative statement became an affirmative assessment by 2005.  “Visible shackling undermines the presumption of innocence and the related fairness of the factfinding process…” Deck v. Missouri, 544 U.S. 622, 630, 125 S. Ct. 2007, 2013 (U.S. 2005).

The science behind the assertion made in Deck was recently relied on came in a federal habeas proceeding where the issue was whether the defendant was injured by being shackled, i.e., whether seeing a murder defendant in chains “had a substantial and injurious effect or influence in determining the jury’s verdict[,]”  the Brecht standard for post-conviction relief.  The appellate court’s assessment here had to be made in light of post-conviction protestations of there being no impact coming from testimony of the actual jurors.

Several jurors recalled at the evidentiary hearing that they had thought Davenport might be dangerous when they saw him in shackles. Another juror recalled that she was sitting closest to Davenport when he testified and a fellow juror had asked her if that made her nervous. She also recalled that there were more guards when Davenport testified because he was not in shackles. But the jurors who testified that they saw Davenport’s shackles also all said that they believed shackling was routine practice given that he was on trial for murder or because he was in pre-trial incarceration. Every juror asked also testified that Davenport’s shackling did not affect their deliberations.


Davenport v. MacLaren, 964 F.3d 448, 453 6th Cir. 2020)(emphasis added)

Rejecting the jurors’ self-professed impartiality, the majority in Davenport first turned to a generalized repudiation of the ‘trust me’ testimony.

If a practice involves such a probability that prejudice will result that it is deemed inherently lacking in due process, like shackling a defendant without case-specific reasons, little stock need be placed in jurors’ claims to the contrary. Even though a practice may be inherently prejudicial, jurors will not necessarily be fully conscious of the effect it will have on their attitude toward the accused.

964 F.3d at 466 (citation omitted).  Importantly for this article, the majority then turned to what it called “voluminous” social science to support this determination, concluding that “[t]his research suggests that the shackling of Davenport, a 6’5″ tall black man weighing approximately 300 pounds, would tend to “prime” racialized presumptions of dangerousness and guilt.”  Id., at 466 n.13.  Because the jury decision at issue -whether the crime was first or second degree murder- was not a ‘slam dunk,’ one, the prejudice could not be ignored.

Intriguingly, the research cited by the majority was not shackling-specific, but instead dealt with the general problem of associating race with criminality, what the majority summarized as “implicit associations between Black and Guilty.”  Id., at 466 n.13.  Yet when confronted with a type of proof where research has shown a clear biasing effect, courts have uniformly ignored the social science.  The is the case with the use of slow-motion video replay.

First, the research.  Repeated studies have shown that slowing down a video when it is played to a decision-maker – be it a juror or, as in one study, experienced soccer referees – increases the perceiver’s assessment that conduct was intentional.

A main characteristic of slow motion is that it affects the impressions of the duration over which real-time events unfold. As suggested by Caruso et al., the temporal modulation of the dynamics creates the perception that the offender has much more time to contemplate his action than he actually does. Therefore, physical contacts and violent actions might be perceived more intentionally and seriously. Indeed, we hypothesized that slow-motion replays could disrupt normal perception of causality, which in turn could influence the perceived duration of the event.

Spitz, J., Moors, P., Wagemans, J. et al. The impact of video speed on the decision-making process of sports officials. Cogn. Research 3, 16 (2018). (last visited September 4, 2020).  An additional concern arises if the video is played in slow motion more than once.  “If viewers’ perceptions adjust such that slow motion appears normal to them after extended viewing, then it is possible that viewers’ perceptions of the amount of time that subjects in video had to act and their evaluations of how intentional the subject’s actions were would also intensify with repeat viewings.”  NOTE: THE NOISY “SILENT WITNESS”: THE MISPERCEPTION AND MISUSE OF CRIMINAL VIDEO EVIDENCE, 94 Ind. L.J. 1651, 1675 (2019).

The impact of repeated viewing is not cured by reminding jurors that they are watching an altered version of the events.

[P]articipants reported similar results even when they were informed, by way of a timer in the video, exactly how much the video had been slowed. And, perhaps most surprising of all, viewers who watched a slowmotion video continued to report a higher degree of intent even after they watched the regular speed video: “allowing viewers to see both regular speed and slow motion replay mitigates the bias, but does not eliminate it.”

Stoughton, POLICE BODY-WORN CAMERAS , 96 N.C.L. Rev. 1363, 1413 (June, 2018).

Yet how have courts responded?  Uniformly by rejecting challenges to slow-motion replay.  A LEXIS search of “slow w/2 motion w/3 video w/12 intent! or prejudic!” (last run September 4, 2020) produced eleven decisions at both the state and federal level.  Of those addressing admissibility, none found an abuse of discretion and disconcertingly not one cited to or otherwise acknowledged the research on the distorting impact slow-motion replay generates.

Some of these decisions may be proper, especially where slow motion was necessary to permit a better view of the perpetrator’s face and therefore allow the jury to determine the identity of the perpetrator or assess whether certain conduct actually occurred such as whether a knife was used in a stabbing rather than slashing fashion.  But time and again the courts also talk of the need to prove intentionality, and then add reasoning that is a- or anti-scientific.  Such sentiments include the following:

  • we find that the probative value of the slow motion footage outweighed any potential for prejudice, particularly given that: the jury was first shown the scenes at normal speed, which allowed it to see the true timing of the events as they transpired; the slow motion footage was clearly marked as such; and the trial court specifically instructed the jury regarding both the purposes for which it was to consider the video footage and the fact that it should not allow the video to inflame their passions against Appellant.Commonwealth v. Cash, 635 Pa. 451, 478, 137 A.3d 1262, 1277 (Pa. 2016)(emphasis added)
  • “As for the prejudicial effect of admitting the slow motion video, the court noted that [t]he jury obviously understood the tape was being played in slow motion rather than in real time,” given that they “saw the tape played at regular speed, twice…”Jones v. Fisher, 2013 U.S. Dist. LEXIS 184948, *29-30 (E.D. Pa. 2013)(internal quotation marks omitted)
  • We have previously approved of a district court’s decision to send tape recordings and a tape player into the jury room during deliberations, and in that situation jurors could replay the tapes as often—or as slowly—as they likedUnited States v. Plato, 629 F.3d 646, 652 (7th 2010)

These may be well-intentioned jurists, but these are ipsi dixit statements of how jurors will be impacted.

What is to be made of these disparate treatments of psychological research?  There is no clear answer.  The problem in the slow-motion cases may have been that of counsel who failed to brief the relevant research, or the need for clarity on issues such as facial identification may have dwarfed any concern over the risks in assessing intentionality.  And is the shackling decision a  product of its time, coming in an era of great concern over racism and implicit bias, concerns not necessarily or as manifestly implicated in the slow-motion cases?

Whatever the reason, the lesson is the same. On a variety of issues of courtroom conduct and evidence, cognitive psychology and social science research should give judges pause before determining how a trial will proceed.  The failure of advocates to proffer such findings and the absence of discussion of them in judicial opinions raises concerns over the reliability of adjudications and whether evidentiary rulings are really just gut-checks based on old tropes.