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In the eyes of the beholder: your client crashed into a stopped vehicle on a straight road under clear skies. So is she at fault? Not necessarily. The science of human perception can help you show how a seemingly avoidable collision was anything but.

Article Excerpt
As the Jones family sat in my office and told their story, none of us could understand how the collision that killed their relative had happened. (1) Just a few nights earlier, Susan Jones had been driving home late at night and ran directly into the side of a tanker truck that had jackknifed, leaving its trailer blocking both lanes of the road.

The tractor had all the required lighting equipment, and the bright chrome trailer displayed more than 40 feet of red-and-white retroreflective tape. The road was flat and straight for hundreds of feet in each direction. The weather on the night of the collision was perfect, and the moon was out. Under these circumstances, how could Susan not have seen the 60-foot chrome cylinder right in front of her in time to stop?

She was killed instantly in the collision, so we can never know for sure what happened during those critical seconds before impact. But the crash scene provided some insight. For example, the only evidence that Susan took any evasive maneuvers was a pair of skid marks beginning just 25 feet in front of the tanker. The crush damage to her vehicle revealed that the speed of the impact was over 40 mph. Combined, these facts made it clear that Susan simply did not see the tanker until she was so close to it that collision was unavoidable. Our mission was to show the jury why.

As plaintiff lawyers, we often handle cases that leave us wondering how someone might not have perceived a hazard in time to avoid it. By understanding the science of how people perceive and react to hazards, we can better explain to juries how accidents occur and why the victim is not at fault.

To understand hazard perception, we must begin with a basic understanding of the anatomy of the human eye. (And my apologies to any physicians, optometrists, or human-factors experts who may be reading this gross oversimplification of the physiology of human sight.) The cornea is the outside of the front of the eye where light enters. The pupil is the dark circle in the center of the eye. The iris is the colored portion of the eye that controls how big the pupil is, which determines how much light is allowed to pass through the lens. The retina is the area on the inside of the back of the eye. As light enters, the lens focuses light onto an area of the retina called the fovea. (2)

The retina has two types of receptor cells: rods and cones. Rods, which are present everywhere in the retina except in the fovea, function primarily in lowlight situations and do not provide color vision. Cones are found mostly in the fovea, operate in situations where more light exists, and provide color vision.

The fovea covers a very small area of the total field of vision, so most of a person's vision is peripheral. For this reason, a hazard usually is initially detected within the periphery and then identified when the person's eyes shift and the object falls within the area covered by the fovea. But to cause this shift, the object must be conspicuous enough to attract the person's attention. In general, the farther away the object is from the foveal area, the harder it is to detect.

When a visual image is projected onto the fovea, neurosignals speed the image to...