Body Worn Video Steering Group

Perceptual Distortion in Deadly Situations

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The topic of perception is usually referred to in the context of body worn video to address the high-adrenaline changes to the body during a threatening situation. In such situations many officers report a variety of conditions such as tunnel-vision, lessened hearing, slowing of motion, plus more.


“Cops are human beings; they react just as others who are involved in stressful life-threatening situations,” says criminologist David Kliger, researching the use of deadly force at the University of Missouri. “This tells us we need to understand how it is that these events are experienced before we can pass judgment on an officer.”

His research suggests that in pre, during, and post, deadly situations 90% of officers experience some kind of perceptual distortion. “The fact is that these distortions occur, and unless there is a video account to check what the officer said, we might not know for sure.”

Attorney Brendan Kelly states “To give a jury more information and more input that may show what happened at a certain time and place can only be a good thing when we’re trying to get to the truth.”

Often, Kelly says, two witnesses can provide statements for the same event but with noticeable disparities, not because one is lying, but their perceptions were different based on a variety of factors, particularly stress.

“It’s the same with police officers”.

Simon Chesterman, writing for The Justice Gap, explains how an officers’ recollection of an event can differ from evidential video footage recorded during an incident:

“The human brain relies on internal sources of information such as thoughts and feelings and external visual and auditory stimulus. Firearms operations can be highly stressful and when facing an armed and dangerous individual the officer’s peripheral vision will involuntarily shut down and they will hone in on the threat. This effect is sometimes known as ‘weapon focus’ or more commonly ‘tunnel vision’. In stressful or traumatic situations some degree of perceptual distortion is inevitable.”

“When your body mobilizes itself to survive, your visual process shifts from a rolling tape to stills. Why? No one knows,” Klinger says.

“[A camera] only captures what it [the situation] looks like, but it doesn’t capture what the officer is seeing or perceiving,” something which should be taken into account when assessing deadly use-of-force. Many agree that body worn video plays a key part in giving greater dimension to a crime scene, providing a ‘look-in’ to the situation as it took place, leading to stronger convictions and sophisticated investigation into the use of deadly force.

The statistics below show the types of perceptual distortion experienced by officers, and their physical responses afterwards. (Source:  2006 National Institute of Justice study)



Body worn video is unlikely to stop the effects that stress has on perception, but will be a reliable witness for any officers who conducts themselves appropriately leading some to speculate that it could reduce negative post-trauma responses.

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