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10 limitations of body cams you need to know for your protection

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    Posted on: October 8th, 2014

    A special report from the Force Science Institute

    The idea is building that once every cop is equipped with a body camera, the controversy

    will be taken out of police shootings and other uses of force because “what really

    happened” will be captured on video for all to see.

    Well, to borrow the title from an old Gershwin tune, “It Ain’t Necessarily So.”

    There’s no doubt that body cameras—like dash cams, cell phone cams, and surveillance

    cams—can provide a unique perspective on police encounters and, in most cases, are

    likely to help officers. But like those other devices, a camera mounted on your uniform or

    on your head has limitations that need to be understood and considered when evaluating

    the images they record.

    “Rushing to condemn an officer for inappropriate behavior based solely on body-camera

    evidence can be a dicey proposition,” cautions Dr. Bill Lewinski, executive director of

    the Force Science Institute. “Certainly, a camera can provide more information about

    what happened on the street. But it can’t necessarily provide all the information needed

    to make a fair and impartial final judgment. There still may be influential human factors

    involved, apart from what the camera sees.”

    In a recent conversation with Force Science News, Lewinski enumerated 10 limitations

    that are important to keep in mind regarding body-camera evidence (and, for the most

    part, recordings from other cameras as well) if you are an investigator, a police attorney,

    a force reviewer, or an involved officer. This information may also be helpful in efforts to

    educate your community.

    (Some of these points are elaborated on in greater depth during the Force Science

    Certification Course. Visit for information on the course. An

    earlier report on body cam limitations appeared in Force Science News #145, sent

    3/12/10. You will find online it at:

    1. A camera doesn’t follow your eyes or see as they see.

    At the current level of development, a body camera is not an eye-tracker like FSI has

    used in some of its studies of officer attention. That complex apparatus can follow the

    movement of your eyes and superimpose on video small red circles that mark precisely

    where you are looking from one microsecond to the next.

    “A body camera photographs a broad scene but it can’t document where within that scene

    you are looking at any given instant,” Lewinski says. “If you glance away from where the

    camera is concentrating, you may not see action within the camera frame that appears to

    be occurring ‘right before your eyes.’

    “Likewise, the camera can’t acknowledge physiological and psychological phenomena

    that you may experience under high stress. As a survival mechanism, your brain may

    suppress some incoming visual images that seem unimportant in a life-threatening

    situation so you can completely focus very narrowly on the threat. You won’t be aware of

    what your brain is screening out.

    “Your brain may also play visual tricks on you that the camera can’t match. If a suspect is

    driving a vehicle toward you, for example, it will seem to be closer, larger, and faster

    than it really is because of a phenomenon called ‘looming.’ Camera footage may not

    convey the same sense of threat that you experienced.

    “In short, there can be a huge disconnect between your field of view and your visual

    perception and the camera’s. Later, someone reviewing what’s caught on camera and

    judging your actions could have a profoundly different sense of what happened than you

    had at the time it was occurring.”

    2. Some important danger cues can’t be recorded.

    “Tactile cues that are often important to officers in deciding to use force are difficult for

    cameras to capture,” Lewinski says. “Resistive tension is a prime example.

    “You can usually tell when you touch a suspect whether he or she is going to resist. You

    may quickly apply force as a preemptive measure, but on camera it may look like you

    made an unprovoked attack, because the sensory cue you felt doesn’t record visually.”

    And, of course, the camera can’t record the history and experience you bring to an

    encounter. “Suspect behavior that may appear innocuous on film to a naïve civilian can

    convey the risk of mortal danger to you as a streetwise officer,” Lewinski says. “For

    instance, an assaultive subject who brings his hands up may look to a civilian like he’s

    surrendering, but to you, based on past experience, that can be a very intimidating and

    combative movement, signaling his preparation for a fighting attack. The camera just

    captures the action, not your interpretation.”

    3. Camera speed differs from the speed of life.

    Because body cameras record at much higher speeds than typical convenience store or

    correctional facility security cameras, it’s less likely that important details will be lost in

    the millisecond gaps between frames, as sometimes happens with those cruder devices.

    “But it’s still theoretically possible that something as brief as a muzzle flash or the glint

    of a knife blade that may become a factor in a use-of-force case could still fail to be

    recorded,” Lewinski says. Of greater consequence, he believes, is the body camera’s depiction of action and

    reaction times. “Because of the reactionary curve, an officer can be half a second or more behind the

    action as it unfolds on the screen,” Lewinski explains. “Whether he’s shooting or

    stopping shooting, his recognition, decision-making, and physical activation all take

    time—but obviously can’t be shown on camera. People who don’t understand this reactionary process won’t factor it in when viewing

    the footage. They’ll think the officer is keeping pace with the speed of the action as the

    camera records it. So without knowledgeable input, they aren’t likely to understand how

    an officer can unintentionally end up placing rounds in a suspect’s back or firing

    additional shots after a threat has ended.”

    4. A camera may see better than you do in low light.

    “The high-tech imaging of body cameras allows them to record with clarity in many lowlight

    settings,” Lewinski says. “When footage is screened later, it may actually be

    possible to see elements of the scene in sharper detail than you could at the time the

    camera was activated.

    “If you are receiving less visual information than the camera is recording under timepressured

    circumstances, you are going to be more dependent on context and movement

    in assessing and reacting to potential threats. In dim light, a suspect’s posturing will

    likely mean more to you immediately than some object he’s holding. When footage is

    reviewed later, it may be evident that the object in his hand was a cell phone, say, rather

    than a gun. If you’re expected to have seen that as clearly as the camera did, your

    reaction might seem highly inappropriate.”

    On the other hand, he notes, cameras do not always deal well with lighting transitions.

    “Going suddenly from bright to dim light or vice versa, a camera may briefly blank out

    images altogether,” he says.

    5. Your body may block the view.

    “How much of a scene a camera captures is highly dependent on where it’s positioned

    and where the action takes place,” Lewinski notes. “Depending on location and angle, a

    picture may be blocked by your own body parts, from your nose to your hands.

    “If you’re firing a gun or a Taser, for example, a camera on your chest may not record

    much more than your extended arms and hands. Or just blading your stance may obscure

    the camera’s view. Critical moments within a scenario that you can see may be missed

    entirely by your body cam because of these dynamics, ultimately masking what a

    reviewer may need to see to make a fair judgment.”

    6. A camera only records in 2-D.

    Because cameras don’t record depth of field—the third dimension that’s perceived by the

    human eye—accurately judging distances on their footage can be difficult.

    “Depending on the lens involved, cameras may compress distances between objects or

    make them appear closer than they really are,” Lewinski says. “Without a proper sense of

    distance, a reviewer may misinterpret the level of threat an officer was facing.”

    In the Force Science Certification Course, he critiques several camera images in which

    distance distortion became problematic. In one, an officer’s use of force seemed

    inappropriate because the suspect appears to be too far away to pose an immediate threat.

    In another, an officer appears to strike a suspect’s head with a flashlight when, in fact, the

    blow was directed at a hand and never touched the head.

    “There are technical means for determining distances on 2-D recordings,” Lewinski says,

    “but these are not commonly known or accessed by most investigators.”

    7. The absence of sophisticated time-stamping may prove critical.

    The time-stamping that is automatically imposed on camera footage is a gross number,

    generally measuring the action minute by minute. “In some high-profile, controversial

    shooting cases that is not sophisticated enough,” Lewinski says. “To fully analyze and

    explain an officer’s perceptions, reaction time, judgment, and decision-making it may be

    critical to break the action down to units of one-hundredths of a second or even less.

    “There are post-production computer programs that can electronically encode footage to

    those specifications, and the Force Science Institute strongly recommends that these be

    employed. When reviewers see precisely how quickly suspects can move and how fast

    the various elements of a use-of-force event unfold, it can radically change their

    perception of what happened and the pressure involved officers were under to act.”

    8. One camera may not be enough.

    “The more cameras there are recording a force event, the more opportunities there are

    likely to be to clarify uncertainties,” Lewinski says. “The angle, the ambient lighting, and

    other elements will almost certainly vary from one officer’s perspective to another’s, and

    syncing the footage up will provide broader information for understanding the dynamics

    of what happened. What looks like an egregious action from one angle may seem

    perfectly justified from another.

    “Think of the analysis of plays in a football game. In resolving close calls, referees want

    to view the action from as many cameras as possible to fully understand what they’re

    seeing. Ideally, officers deserve the same consideration. The problem is that many times

    there is only one camera involved, compared to a dozen that may be consulted in a

    sporting event, and in that case the limitations must be kept even firmer in mind.

    9. A camera encourages second-guessing.

    “According to the U. S. Supreme Court in Graham v. Connor, an officer’s decisions in

    tense, uncertain, and rapidly evolving situations are not to be judged with the ‘20/20

    vision of hindsight,’ ” Lewinski notes. “But in the real-world aftermath of a shooting,

    camera footage provides an almost irresistible temptation for reviewers to play the

    coulda-shoulda game.

    “Under calm and comfortable conditions, they can infinitely replay the action, scrutinize

    it for hard-to-see detail, slow it down, freeze it. The officer had to assess what he was

    experiencing while it was happening and under the stress of his life potentially being on

    the line. That disparity can lead to far different conclusions.

    “As part of the incident investigation, we recommend that an officer be permitted to see

    what his body camera and other cameras recorded. He should be cautioned, however, to

    regard the footage only as informational. He should not allow it to supplant his first-hand

    memory of the incident. Justification for a shooting or other use of force will come from

    what an officer reasonably perceived, not necessarily from what a camera saw.”

    [For more details about FSI’s position on whether officers should be allowed to view

    video of their incidents, see Force Science News #114 (1/17/09). You will find online it


    10. A camera can never replace a thorough investigation.

    When officers oppose wearing cameras, civilians sometimes assume they fear

    “transparency.” But more often, Lewinski believes, they are concerned that camera

    recordings will be given undue, if not exclusive, weight in judging their actions.

    “A camera’s recording should never be regarded solely as the Truth about a controversial

    incident,” Lewinski declares. “It needs to be weighed and tested against witness

    testimony, forensics, the involved officer’s statement, and other elements of a fair,

    thorough, and impartial investigation that takes human factors into consideration.

    “This is in no way intended to belittle the merits of body cameras. Early testing has

    shown that they tend to reduce the frequency of force encounters as well as complaints

    against officers.

    “But a well-known police defense attorney is not far wrong when he calls cameras ‘the

    best evidence and the worst evidence.’ The limitations of body cams and others need to

    be fully understood and evaluated to maximize their effectiveness and to assure that they

    are not regarded as infallible ‘magic bullets’ by people who do not fully grasp the

    realities of force dynamics.”


    Our thanks to Parris Ward, director and litigation graphics consultant with Biodynamics

    Engineering, Inc., for his help in facilitating this report.


    For more information on the work of the Force Science Institute, visit To reach the Force Science News editorial staff please e-mail: