Psychology in Criminal Investigation

Source: Image Taken by Matthew Sharps

Criminal investigations must be successful if the criminal justice system is to function. Yet there are a variety of psychological processes that can interfere with successful investigative procedures. One of these is cognitive tunneling, a phenomenon related to tunnel vision.

In tunnel vision, of course, we focus on things that present themselves toward the center of our visual fields at the expense of other things that are more peripheral in our view. This process can result in catastrophic consequences in tactical situations in law enforcement and elsewhere, but tunnel vision also has a cognitive analog, cognitive tunneling, in which we focus on core ideas to the exclusion of more peripheral prospects, prospects that might be critically important to the successful resolution of any given problem.

Cognitive tunneling is more likely to have important consequences in situations in which we are physiologically and psychologically aroused. As the body and brain adjust to stress, fewer resources become available to the prefrontal cortex, our major center of judgment and decision. Under these conditions, we are less likely to notice peripheral hazards in our visual fields of view (Artwohl and Christensen, 2019; Sharps, 2022) and less likely to process more peripheral prospects in our mental consideration of given situations as well (Sharps, 2022, 2024).

We can see these processes operating in our everyday lives, of course. In a crowded, stressful store, we may become so focused on the appliance that we intended to buy when we entered the shop that we may completely fail to notice better sales advertised on other appliances. We may also fail to consider, at a cognitive level, whether another appliance might be cheaper or more suitable for our purposes. As another example, many couples experience similar processes in the interpersonal realm, as heated arguments over the same issues are repeated again and again, with no new prospects for resolution considered or proposed. Even at relatively low levels, stress can reduce our visual and cognitive flexibility. Cognitive tunneling operates in many walks of life.

Yet these everyday difficulties are frequently eclipsed, in the severity of their consequences, in the world of criminal justice. Many case examples could be drawn, but the specific tragic and infamous case of the so-called Washington Snipers in 2002 is a good example.

The case is considered in depth elsewhere (Horwitz and Ruane, 2003; Sharps, 2024), but in brief, two men engaged in an ideology-based reign of terror in the area around Washington, DC, for more than three weeks, killing or wounding 13 people from a concealed sniping position in their car. Their vehicle was a blue Chevrolet Caprice. Such a vehicle had already been reported in connection with the case; but these reports were essentially shouted down, and effectively ignored, because of a new and relatively detailed eyewitness report, which turned out to be completely inaccurate, that the shooters employed a white box truck at the scene of one of the shootings.

The white-box-truck mania
Small box trucks and minivans are ubiquitous in virtually every metropolitan area of the United States, and the businesses which employ them, for a wide range of commercial purposes, often choose white or other light colors for these vehicles; the dust of the streets is generally less noticeable on these colors than on many darker hues, so the vehicles typically don't need to be washed as often, saving money. Therefore, when you look around in an urban setting, whether or not there's been a shooting in the area, it’s a good bet that you'll see some small, light-colored van or box truck.

And, of course, people did. All over the place. Law enforcement began to receive many calls about mysterious white or off-white box trucks, which became conflated with pale minivans very early on as the case progressed. With more press coverage, these reports began to multiply. Authorities strained their resources to a very high level in an attempt to investigate all of these reports. This investment in time and finances, together with the ubiquity of the reports of these vehicles, resulted in a level of cognitive tunneling so profound that the earlier reports of the blue Chevrolet were essentially ignored, overwhelmed by a kind of white-box-truck mania. The Washington snipers themselves further compounded the problem by deliberately setting up killings near parked pale vans and box trucks to enhance the confusion; and as the killings continued unabated, the stress on law enforcement officers increased dramatically, perhaps contributing to the cognitive tunneling involved.

We will probably never know if this cognitive tunneling on the wrong vehicle type prolonged the killing spree, but it certainly did not accelerate the apprehension of the terrorists. The case was ultimately solved after the media found out about the earlier reports of the blue Chevrolet Caprice and, against some opposition from law enforcement, broadcast this information. In a somewhat bizarre coincidence, a man who drove a white van for work, but also happened to own a blue Chevrolet Caprice, heard these media reports. From the standpoint of his own involvement with both types of vehicle, he deliberately went on the lookout for the actual vehicle driven by the terrorists; and to continue the amazing chain of coincidence, he spotted the snipers’ blue Caprice at a rest stop. His discovery enabled law enforcement to make the arrest.

It is conceivable that without this weird series of coincidences, the Washington terrorists might have joined D.B. Cooper and other unknown criminal perpetrators in the realm of the undetected criminal and the unsolved crime. Successful criminal investigation involves a focus on important evidence, but if that focus is diverted to irrelevant or misleading evidence, cognitive tunneling may occur with very deleterious consequences to the entire case. An awareness of the relevant psychological processes may be of great benefit both to effective law enforcement and to the society that depends on it.