10/16/2014 04:28 pm ET Updated Dec 16, 2014

More Than Meets the Eye: How Video Evidence Alters Our Decision Making

Craig F. Walker via Getty Images

This fall has seen a widespread call from the public, politicians, and even the White House, in favor of body-worn cameras for police. In the wake of fatal shootings like the one in Ferguson, MO in August, policy-makers argue that one vital benefit of police head or chest-mounted cameras is the ample evidence they can provide for legal proceedings (1). It seems that if we could just look at the videotape, we would know with certainty exactly what happened.

People have incredible faith in their visual experience -- a faith shared by the legal system. Video evidence is more vivid, more emotionally arousing, and more credible than other forms of evidence (2). In fact, vision is considered so critical to the process of making legal decisions that the blind are one of the only classes of persons legally allowed to be barred from jury service (3). Indeed, arbiters of justice often rely on what they see. In a recent Supreme Court decision that featured video from a police dashboard camera, Justice Breyer, in his majority opinion wrote, "If... I see with my eyes that is what happened, what am I supposed to do?" (4). Even among Justices in the highest court in the land, video evidence seems to allow for a single, objective conclusion.

However, watching video evidence does not necessarily ensure a unified or accurate understanding of the facts of a case. In fact, how people watch evidence may exaggerate an "us versus them" divide already present in the legal system. In new research, we found that people actually watch evidence in different ways, which polarizes their judgments about guilt and innocence. In a forthcoming issue of the Journal of Experimental Psychology: General, we and our co-authors, Kristin Schneider and Tom Tyler, found that the more that people acting as jury members looked at a defendant, the more divided their legal decisions about him became (5). In three studies, we showed people videos depicting an altercation between a man who was part of their social group and a man who was a part of another group, or out-group. In these fights, it was unclear who was in the right and who was in the wrong. Participants, acting as mock-jurors, assigned punishment to the out-group defendant. Without participants' awareness, we monitored their eye movements using infrared eye-tracking technology, allowing us to test the effects of where people looked on how severely they punished a defendant.

In our first two studies, we measured decisions to punish police officers engaged in altercations with civilians. We showed participants police dashboard camera footage of real fist fights between an officer and a civilian. We either measured how many times they looked at the officer or specifically told them to focus on the police officer or the civilian. We found that among those people that looked most often at the officer, social identification with police determined punishment. People who felt strongly identified with police were much more lenient toward the officer than people less identified with police. Individuals who looked most often at the officer were similarly divided about how incriminating his actions were. However, those who looked less frequently at the officer punished him similarly and found his actions equally incriminating, regardless of their feelings of identification.

Yet these results are not specific to cases involving police and the populace. The impact of group affiliations on jury decisions is a more general process that can play out for various kinds of groups to which people belong. In a third study, we demonstrated this by having people complete a fake personality test, described as a valid way of determining "Blue" or "Green" identities. Unknown to participants, these group assignments were actually randomly determined by a flip of a coin. Participants then watched surveillance footage of a fight between two college students, one in a blue shirt and the other a green shirt. Participants decided how much to punish each student, imagining themselves as the university disciplinary committee. Only among people who looked most often at their out-group (e.g. the Blue man, for Green participants), participants more strongly identified with their own group punished the out-group defendant more than participants who did not feel strongly connected to their group. Even more dramatically, patterns of eye movements changed participants' actual memory of events. Looking at one defendant more intently not only did not guarantee convergent understanding of what happened -- it actually undermined it.

Like our research, other contemporary work shows how video may encourage bias and impair accurate understanding of case facts. One study found that watching video evidence can actually change what individuals know to be the objective truth of an event. Psychologists confronted participants about having stolen fake money during a previous experimental session -- something both the experimenter and participants knew had not occurred. Experimenters then showed some participants doctored footage of themselves committing the theft. Despite knowing better than anyone that they hadn't taken the money, participants who saw the doctored footage were more likely than those who merely knew footage existed to report believing they had acted illicitly. Moreover, these people were also more likely to actually sign a written confession attesting to their crime (6). Video evidence can foster reasonable doubt where none should exist or inflate certainty in the face of ambiguity.

Some research has gone so far as to question the confidence extended to video in real legal cases. In the case of Scott v Harris, the Supreme Court overturned lower court decisions, finding an officer not culpable of excessive force after he ran a civilian's car off the road and paralyzed him. The Court based its decision largely on dashboard camera evidence, suggesting that no "reasonable juror" could have concluded otherwise after watching the videotape. Researchers at Yale University took up that challenge, showing the real case footage to over a thousand potential jurors from all over America (7). Marked group differences emerged in decisions about legal culpability. Whites and Blacks, liberals and conservatives, individualists as compared to community-oriented people, all showed significant divisions in their appraisals of the evidence. Our research suggests that selective visual attention to the evidence may be the process by which different judgments emerge among people differently identified with the parties involved.

We do not propose that collecting video evidence is bad. Indeed, as long as evidence is more probative than prejudicial, more evidence is generally a good thing. Rather, ours is a cautionary tale. The ways in which people watch video evidence can create problems by exacerbating biased decisions. We suggest that more scrutiny be given to how jurors actually watch the evidence. If where people look can promote bias, directing attention might also be used to reduce it. In a dynamically visual age, modern instructions must consider new ways to ensure that justice remain "blind."

Yael Granot is a PhD candidate in Social Psychology at New York University and Emily Balcetis is Assistant Professor of Psychology at New York University.



1. Miller, L., Toliver, J. & Police Executive Research Forum (2014). Implementing a body-worn camera program: Recommendations and lessons learned. Washington, DC: Office of Community Oriented Policing Services.

2. Sherwin, R. K., Feigenson, N., & Spiesel, C. (2006). Law in the digital age: How visual communication technologies are transforming the practice, theory, and teaching of law. Boston University Journal of Science and Technology Law, 12, 227-273.

3. U.S. v. Watson, 483 F.3d 828 (D.C. Cir. 2007)

4. Scott v Harris, 127 S. Ct. 1769, 1773 (2007). Transcript of oral argument, 27.

5. Granot, Y., Balcetis, E., Schneider, K. E., & Tyler, T. R. (2014). Justice is not blind: Visual attention exaggerates effects of group identification on legal punishment. Journal of Experimental Psychology: General. Advance online publication.

6. Nash, R. A., & Wade, K. A. (2009). Innocent but proven guilty: Eliciting internalized false confessions using doctored-video evidence. Applied Cognitive Psychology, 23, 624-637.

7. Kahan, D. M., Hoffman, D. A., & Braman, D. (2009). Whose eyes are you going to believe? Scott v. Harris and the perils of cognitive illiberalism. Harvard Law Review, 122, 837-906.