In View: Interpreting BWC Video Footage

Understanding the Practical Aspects of Interpreting Video Footage

Seth Stoughton, Assistant Professor at the University of South Carolina School of Law

Following the intense public scrutiny of law enforcement since the summer of 2014, community members, politicians, and police executives alike have called for the adoption of body-worn camera (BWC) systems.  There have been a variety of reasons offered in support of body-worn cameras, all of which coalesce around advancing three potential benefits: a signaling benefit, a behavioral change benefit, and a documentation benefit.  Agencies and executives that are considering or implementing BWC programs may want to contemplate how different policies and procedures will advance or undermine these potential benefits.  This commentary briefly addresses the first two benefits, and then discusses in more depth some of the practical challenges that relate to the documentation benefit: specifically, the difficulty of accurately interpreting BWC video.

Signaling.  By adopting a BWC system, police agencies are sending the message that they are receptive and responsive to community concerns, and that they are committed to bolstering transparency and accountability.  These signals are particularly important today: according to a 2015 Gallup poll, public confidence in policing is at its lowest point since 1993; a bare majority of Americans report confidence in the police, and an unprecedented number of people report no or very little confidence in policing.  An agency’s adoption of a BWC system can be an encouraging sign for a skeptical public, but agencies should not assume that the adoption, by itself, is sufficient to restore public trust.  Whether a BWC program remains a signal of transparency and accountability will depend on agencies’ policies and procedures.  Counterintuitively, BWCs can be implemented in a way that hurts public trust.  If officers routinely fail to record incidents that should be recorded, for example, or if the agency refuses to release video footage, particularly footage of high-profile events like officer-involved shootings, for a prolonged and indefinite period of time, instead of increasing public support, BWCs may seriously undermine police/community relations.

Behavioral Change.  There is a growing body of research suggesting that body-worn cameras have some effect on behavior.  Thus far, the bulk of the research has focused on BWCs possibly having a moderating effect on civilians and officers alike that can contribute to reductions in  assaults against officers, use-of-force incidents, and civilian complaints.  There may also be unanticipated behavioral changes, such as an increase in discretionary arrests. These behavioral changes and others may be explained by the “observer effect”: we change the way we behave when we know we’re being observed.  Exactly what effect body-worn cameras will have on officer behavior, then, will depend heavily on how the technology is implemented—particularly on automatic recording mechanisms or mandatory recording policies—and the policies on supervisor review.  What is less clear is the extent to which, over time, body-worn cameras will have a long-term effect on behavior.  As patrolling with BWCs becomes part of an officer’s typical operating environment, the observer effect may dissipate over time. In the same vein, if agencies and front-line supervisors become accustomed to reviewing body-worn camera footage, we may see longer-lasting behavioral changes than we would if the video footage goes largely unseen.

Documentation.  Perhaps the single most important benefit that body-worn cameras offer is the ability to provide viewers with information that they would not otherwise have.  Community members have called for BWC systems in large part because they want to have—and they want supervisors and police executives to have—more information about how officers are conducting themselves.  Police executives, meanwhile, value the way that BWC footage can educate community members about the dynamic situations that officers deal with, not to mention the value that video has as evidence in administrative proceedings, criminal trials, and civil litigation.  These benefits are real, but they will not apply in all cases, nor will they be consistent across different types of cases.  Further, the adoption and implementation of a body-worn camera system will not automatically improve documentation; a poorly implemented system can reduce the accuracy of information that police supervisors, prosecutors, and juries rely on.  In the following paragraphs, I highlight a few of the practical challenges of interpreting body-worn camera footage that policymakers should consider as they develop implementation strategies for this technology.

BWCs are cameras, nothing more.  This may be an obvious point, but it bears thinking about.  Cameras take in limited information, and they do not see things the way people do.  A camera’s field of view (the extent of the visible image) is both narrower and broader than a human’s field of view.  Narrower because cameras have less range than the human eye.  Taser’s Axon Body camera, for example, has a 130° horizontal field of view, while its Axon Body 2 has a 142° field of view.  Humans, in contrast, have close to a 200° horizontal field of view, significantly wider than either BWC system.  And broader because cameras capture more information in that range than the human eye can.  Everything a camera sees is in focus.  That is certainly not the case for the human eye: our central angle of view is 40-60°, and the angle we keep in sharp focus (the fovea) is far narrower.  That disconnect between what the camera can see and focus on and what an officer can see and focus on means that sometimes officers will see things that aren’t on camera (e.g., when the camera is pointed in the wrong direction), and sometimes the camera will record things that officers may not see themselves (e.g., when the officer’s vision is focused on one of the many things that the camera sees at the time).  Field of view is important for another reason: a camera lens can affect the viewer’s perception of distance.  A camera with a narrow field of view will make someone look closer than a camera with a wide field of view does, even when the video is taken from the same position.

In addition to the limitations of BWC equipment, individuals reviewing video footage also have to contend with the limitations of the human brain, including cognitive biases that affect our perceptions.  Cognitive biases are the psychological equivalent of eyeglasses that we don’t realize we’re wearing: we receive information about the world through a lens without consciously realizing how that lens affects our interpretation. “Camera perspective bias,” for example, refers to our brain’s tendency to exaggerate the causal effect of something merely because it is more visually prominent or noticeable than other factors (a form of what cognitive psychologists call “illusory causation”).  Daniel Lassiter at Ohio University has studied camera perspective bias in the context of police interrogations for years, finding that the angle from which video is taken can dramatically affect viewers’ interpretations, even when those viewers are trained police officers or experienced judges.  Body-worn cameras will be used well outside the confines of the interrogation room, but because they are mounted on an officer and face the individuals that the officer interacts with, camera perspective bias may affect viewer’s perceptions of whether someone is acting voluntarily or being coerced, whether someone is resisting or compliant, and why someone is doing what they are doing.

Body-worn camera footage can be particularly prone to misinterpretation in the context where video is often viewed as needed the most: use-of-force incidents.  This misinterpretation stems in large part from something I call “deceptive intensity,” a non-scientific term that I use to describe how video can appear more intense both by exaggerating movement and by providing misleading information as to distance, relative height, and other factors. 

To understand how this works, take your cell phone camera, start recording a video, , and then put it against your forehead so that the camera is facing roughly in the same direction that you’re looking.  Start recording.  Keeping your eyes fixed on one spot, move your head around so that you’re spelling your full name in the air with the tip of your nose as fast as you can.  If you’re like most people, whatever you’ve fixed your eyes on will stay pretty much in focus.  That’s because of the vestibulo-ocular reflex, which stabilizes images on your retina by compensating for your movement.  Now watch the video.  The movement in the video footage likely looks exaggerated compared to what you saw when you moved your head around.  That’s because your eyes and brain cannot compensate for the movement of the camera the way they did for the movement of your head. 

Other factors, too, can contribute to deceptive intensity, including the way a chest-mounted camera can make individuals whom the officer is physically close to look taller and broader than they actually are.  To experience that firsthand, stand within arm’s reach of someone and look them in the eye.  While they remain standing, bend your knees until your eyes are where your chest was when you were standing – the person in front of you will look substantially taller than they did when you were standing up straight.  Hollywood directors have intentionally used these and other visual tricks for years to affect audience interpretation, but body-worn camera footage isn’t intended to be entertaining or to promote a particular interpretation; it can fulfill the potential benefit to documentation only when it is either accurate or its inaccuracies are well understood.

We tend to think of video footage as more comprehensive, accurate, and precise than other forms of evidence.  None of those things are necessarily true.  Footage from BWC systems will play an increasingly important role in administrative and judicial proceedings, which makes it even more important to understand the practical challenges of interpreting video evidence.

Seth Stoughton is a law professor at the University of South Carolina and a former police officer.  His work focuses on the regulation of policing, including the use of force and police-community relations.

This project was supported by Grant No. 2015-DE-BX-K002 awarded by the Bureau of Justice Assistance. The Bureau of Justice Assistance is a component of the Department of Justice's Office of Justice Programs, which also includes the Bureau of Justice Statistics, the National Institute of Justice, the Office of Juvenile Justiceand Delinquency Prevention, the Office for Victims of Crime, and the SMART Office. Points of view or opinions in this document are those of the author and do not necessarily represent the official position or policies of the U.S. Department of Justice.