The Devastating Effect of “Tunnel Vision” in Criminal Investigations

[Part 4 of a series on: The Common Causes of Wrongful Convictions]

Perhaps you are familiar with this common experience: you had never paid very much attention to a particular make and model of motor vehicle, and you had hardly noticed any of them on the road. Then you began the process of buying a new car for yourself, and when you were shown that model you become interested in it. Suddenly, wherever you went you saw them; they seemed to be everywhere!

This quite normal human tendency is related to what psychologists refer to as “confirmation bias”. Confirmation bias is a kind of selective thinking in which a person is more likely to notice or search for things that confirm their theory or belief. So, in our stated example, your growing conviction is that a particular car is good, therefore probably popular, so your mind searches for the evidence to prove it.

Another closely related tendency is what we call “tunnel vision”. Tunnel vision is the result of our mind narrowing its focus to a limited range of possibilities so that alternatives are not considered. Whilst this may be acceptable, or mildly inconvenient, in many areas of life, it has disastrous effects in the criminal justice system. When not checked it leads investigators, prosecutors, judges and defense lawyers to focus on a particular conclusion, while eliminating from the investigation any alternative suspects or theories, and even any contradictory evidence.

A well-documented example of tunnel vision reported on The Police Chief website (an online magazine of The International Association of Chiefs of Police), is the case of Rachel Nickell. The 23-year-old was found murdered on Wimbledon Common, London, in July 1992. Her throat had been cut, and she had been stabbed 49 times. New Scotland Yard detectives received a tip implicating an eccentric man named Colin Stagg. For an entire year he became the focus of their investigation; an investigation that culminated in a covert “sting” operation using an undercover police woman to try and entrap Stagg.

When the case came to trial in 1994, the judge dismissed much of the prosecution’s evidence saying, “I am afraid this behavior betrays not merely an excessive zeal, but a substantial attempt to incriminate a suspect by positive and deceptive conduct of the grossest kind.” The charges were subsequently dropped, and Stagg was released.

Several years later, DNA testing proved that the real murderer was Robert Napper, a convicted psychopath already committed to a prison mental institution for murder and rape. He had not been adequately considered in the investigation because of the police focus on Colin Stagg – an innocent man.

Tunnel vision is a leading cause of wrongful convictions. In fact, it is an underlying problem that leads to the employment of other causes. Because the police are focused exclusively on one prime suspect, they may lead witnesses to make false identification, confessions may be coerced, the perjury of “snitches” sought, and so on.

While such wrongful convictions of innocent people are a tragedy that must be vigilantly guarded against, there is also another all-too-common and terrible result of tunnel vision. When investigators fail to consider all the evidence, and all the possibilities, it often leads to the real perpetrators never being found. They are excluded from the investigation because officers are focusing elsewhere. The statistics underline this problem: there were approximately 16,000 homicides annually in the United States between 2000 and 2009, with only around 63% of the crimes being solved. So, on average, 16 murders occurred every single day that were never solved and the perpetrators never brought to justice.

What Can Be Done?

This may be the most difficult cause of wrongful convictions to solve by reforms. Requiring actors in the criminal justice system to keep an open mind is subjective and almost impossible to superintend. More must be done, however, to train investigators and prosecutors to recognize and avoid the dangers of tunnel vision.

Sherene G.

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