Force Science #218

I. "Looming": Important consideration when cops fire at moving cars

Skepticism often arises when officers shoot at vehicles they claim were about to run them over. Questions range from "Why didn't the cop just jump out of the way?" to "How come his estimate of the car's speed is so much higher than that of other witnesses at the scene?"

The answers may lie with a perceptional phenomenon called "looming."

This quirk of the mind is now explained in detail in the Force Science certification course and was touched on recently by Dr. Bill Lewinski, executive director of the Force Science Institute, during a presentation on research findings relevant to law enforcement at the annual conference of the Illinois Homicide Investigators Assn.

Looming, Lewinski told the conference's 500 attendees, is an illusion that occurs when a person (an officer in this context) is standing in the path of an approaching vehicle. Each time the gap between the officer and the oncoming car closes by half, the space occupied by the image of the vehicle in the officer's visual field roughly doubles.

"This exponential enhancement--a seemingly explosive rate of growth--is well documented in scientific literature," says Chris Lawrence, the Force Science instructor who teaches looming in the certification course. An officer-safety faculty member at one of North America's largest police training facilities, Lawrence has measured the effect in his own experiments with camera images.

"Because the vehicle appears to be growing dramatically in size, it may seem to be coming at a faster speed than it actually is," Lawrence explains. "The targeted officer may falsely sense that he or she has no time to leap clear, and start shooting instead. Officers are conditioned in training to resort to their firearm in the face of what appears to be an imminent lethal threat.

"Later when the officer reports that the vehicle was bearing down at an inescapable speed, problems may arise. That's because witnesses who are viewing the vehicle from the side won't experience the looming effect. The car will remain essentially the same size as it crosses their visual field, and they'll tend to judge its speed differently. That discrepancy may make the victim officer appear to be lying to justify his use of deadly force."

Details of how looming works get complicated, but the basic phenomenon is important for investigators to know about, Lewinski says, and to be able to articulate in court and before review boards.

Lawrence reports that he and Lewinski currently are working on the best way to demonstrate the phenomenon to triers of fact. The result, Lawrence says, "should help officers in certain controversial encounters where they've shot at vehicles moving toward them."