Cognitive Tunnel Vision Biases and Their Detrimental Affect on Prosecutorial Evidentiary Evaluation

The purpose of this letter is to alert and educate law-enforcement, particularly those engaged with post-conviction “conviction integrity unit” panel evaluations, to the problems involving various kinds of psychological cognitive biases.

Psychological cognitive distortions such as “confirmation bias”, “hindsight bias”, “outcome bias”, and a host of other psychological phenomena result in a general “tunnel vision”. These are the product of multiple processes and pressures and make some degree of tunnel vision inevitable. Normative pressures on police, prosecutors, the courts, and even defense attorneys amplify those natural tendencies. Instead of countering those pressures and tendencies, institutional features of the criminal justice system inevitably institutionalize these biases.[1]

It is especially true that that these biases are magnified in cases of violence against children.  The sensitive nature of the charges; a natural desire to err on the side of protecting the children; the very heinous and emotionally charged nature of such crimes; all tend to distort otherwise ambiguous facts, and intensify these naturally developing prejudices.

Julius Caesar famously said, “Homines fere credunt libentur id quod volunt”, observing that “people easily believe that which they want to be true.” 

I.        Introduction: On Prevalence

The psychological biases to which we refer have been the subject of extensive study by experimental psychologists across a spectrum of professionals and many decades. Nonetheless the tendency of humans toward such biases has been obvious to those willing to objectively observer since time immemorial. What has not been necessarily obvious prior to the study by modern science is the extent to which these biases can operate outside the scope of conscious recognition, as well as the variety of circumstances which intensify the effects of these presumptive biases.[2]

Outlining the multifaceted ways in which psychological biases infects police investigations, district attorney’s offices, and judicial proceedings is not intended to make a value judgment about the nature or qualities of police and prosecutors. Instead we wish, to some degree at least, to merely acknowledge the natural tendencies that can—and do—influence anyone’saccess and interpretation of data. Police, prosecutors, and judges are not bad people because they are affected by tunnel vision; they are merely human.

The intrinsic state of these psychological biases and distortions does not absolve players in the criminal justice system from responsibility of an obligation to attempt overcoming them. Rather, to the contrary, it demands that we become aware of these cognitive processes and the tunnel vision they produce, so we may search for ways to neutralize them.[3]

It should be kept in mind that in the social sciences the term “bias” is value neutral. It merely describes a situation in which any errors that might be made are skewed in one direction or another, as opposed to a situation of random error, where errors have no directionality.[4]

An initial step towards addressing these problems is awareness of multiple causes and expressions. Serious efforts must be made to identify these biases, or the tendencies of the criminal justice system that contribute to their occurrences at every stage in the life of a criminal case, including, and especially, post-conviction integrity unit reinvestigation efforts.

Normative tunnel vision does not end after the conclusion of a conviction.  The distortion intensifies as cases proceed through appellate and post-conviction stages.  That is not to say that procedural rules require situations of tunnel vision during post-conviction review, or to say that such rules are necessarily flawed; good reasons may justify the increasing hostility to claims of innocence as appeal review works its way through the system. However, the effect those rules have on reinforcing tunnel vision biases—and thus on sustaining the conviction of those innocent and wrongfully convicted—must be acknowledged and understood.[5]

II.        Why This Is Especially Important for Conviction Integrity Review Units to be Aware of While Conducting an Investigation

A prosecutors’ assessments of a case review placed before them can be flawed both by the information provided as well as the feedback they receive. Law enforcement prosecutors are particularly vulnerable to distortions based on the types of information their role in the process provides them access. There is a problem of hidden, or absent, data, which is often cited in studies of cognitive error, and can distract actors in the criminal justice system. Various psychological biases impede a person’s ability to rationally and accurately assess both the significance and reliability of information, or to use all information available to them before reaching generalized conclusions. This tendency is exacerbated when crucial information is unavailable.  The lack of complete investigation is a constant hurdle for all parties involved given lack of adequate resources, a dedication beyond that which the system can generally bear the burden, or where full information is simply hidden or absent for various situational reasons.[6]

Conviction integrity units are often confronted with complicated situations involving “reluctant witness” syndrome.  There is an assumed finality of a conviction from the viewpoint of witnesses involved in the criminal process. Post-conviction review boards are sometimes confronted with untangling decade’s old entrenched beliefs.  Examples have shown that it is very difficult to revisit eye witness testimony in a post-conviction setting.

Witness memories have a tendency to latch onto an often small, perhaps ancillary memory, which over time has grown in stature, often crushing any lingering doubt as to the validity of the conviction or guilt of the defendant.  These memories will often be factually insignificant in that they will not relate directly to any observation of the charged crimes to which there is grand jury testimony.  Witness memory works tirelessly to justify away any potential belief or support for the credibility of the wrongful conviction claim.

As much as all parties involved would like to believe otherwise, prosecutors receive only incomplete pictures of their cases. Tunnel vision consistently shapes the information upon which prosecutors base their judgments, or develop leads which focus police on a suspect, or a series of interconnected piece of evidence, and then develop further evidence supporting that suspect or theory, disregarding inconsistent or disconfirming evidence. 

Prosecutors enter the process via the evidence generated by the police investigation, and are rarely privy to any evidence relating to alternative suspects who were rejected too quickly; about eyewitnesses who failed to identify the defendant; or about other disconfirming evidence that police dismissed as insignificant.[7]

III.        Primary Categories of Biases

   A.        Tunnel Vision

Tunnel vision is the product of a variety of cognitive distortions that can impede accuracy in what we perceive and in how we interpret what we perceive. The tendency toward tunnel vision is partly innate; it is part of our psychological makeup. It can lead investigators, prosecutors, judges, and even defense councils to focus on a particular conclusion and then filter all evidence through a tinted lens provided by that assumption.[8]

Tunnel vision is a natural human tendency that has particularly pernicious effects in the criminal justice system. By tunnel vision, we mean that compendium of common heuristics and logical fallacies to which we are all susceptible, that lead actors in the criminal justice system to focus on a suspect, select and filter the evidence that will ‘build a case’ for conviction, while ignoring or suppressing evidence that points away from guilt.[9]

Once these filters are in place all information supporting such an adopted conclusion is elevated in significance, viewed as consistent with the other surrounding evidence, and deemed primarily relevant and probative. Any evidence inconsistent with the presumptive theory is often overlooked, dismissed, deemed irrelevant, incredible, or unreliable.[10]

Psychologists analyze tunnel vision as the product of various cognitive biases such as confirmation bias, hindsight bias, and outcome bias.

   B.        Confirmation Bias

Confirmation bias, as the general term is used in psychological literature, typically connotes the tendency to seek or interpret evidence in ways that support existing beliefs, expectations, or hypotheses. The bias has several expressions. In part, the bias reflects that, when testing a hypothesis or conclusion, people tend to seekinformation that confirms their hypothesis and to avoid information that would disconfirm their hypothesis.[11]

Ongoing studies have repeatedly documented confirmation biases, having found that investigators often seek information in a manner which increase their confidence in a prior belief or hypotheses—even when they have no vested interest in those hypotheses.[12] 

Confirmation bias is especially worrisome and prevalent when it relates to interviewing witnesses.  It should be noted that when evaluating the reliability of witness testimony the post-conviction review process must sometimes consider a potential double-filtering which is occurring.  First through the memory imperfections of the witnesses themselves, and second through the potential tunnel vision judgment of the interviewer. 

The empirical research demonstrates that people not only seek confirming information, but they also tend to recall information in a biased manner. Memory recall when revisiting information previously obtained tends to function in biased ways, giving preference to information that tends to confirm presented hypothesis or belief. In addition to seeking and recalling confirming information, people also tend to give greater weight to information that supports existing beliefs than to information that runs counter to them. Put simply: people tend to interpret data in ways that support their prior beliefs. Contemporary research demonstrates that all people are to some degree always incapable of evaluating the strength of evidence independently of their prior beliefs.[13] 

While biases affect the acquisition and interpretation of information, and thereby cloud rational or logical evaluations of hypotheses or conclusions to reflect new information, there are natural tendencies which people resistant evidence that wholly undermines their initial hypotheses even in the face of new change. This phenomenon, known as “belief perseverance” or “belief persistence”, produces intractable beliefs and opinions. People are naturally disinclined to revisit or revise initial conclusions or beliefs, even in extreme circumstances of overwhelming contradictory revisionist evidence or information which undermines those earlier conclusions. Law enforcement are especially more likely to distrust information which conflicts with preexisting beliefs (or judicially established “fact”) and are personally and professionally inclined to interpret ambiguous information as supporting rather than disconfirming their original beliefs. People can be quite facile at explaining away events that are inconsistent with their established beliefs.[14]  

    C.        Hindsight Bias: “Where there is smoke there is fire,” or “Something must have happened.”

Hindsight bias results from the fact that memory is a fluid process of construction and reconstruction. Memories do not germinate from our brains fully formed. They are assembled piece by piece from information as we recall events. These pieces of information, regardless of the event or situation, are being constantly updated and replaced by our brains with new information.  This updated information is then relied upon each time we are called upon to reconstruct a relevant memory.  This process results in the appearance of the ultimate conclusion being a preordained conclusion.[15]  

During this process, evidence consistent with the reported outcome is elaborated, and evidence inconsistent with the outcome is minimized or discounted. The result of this rejudgment process is that the given outcome seems inevitable or, at least, more plausible than alternative outcomes. Understood another way, the process is one in which an individual reanalyzes an event so that the early stages of the process connect causally to the end.[16] 

Scholarly research has repeatedly shown that when viewed through the passage of time people tend to consider that an eventual outcome was inevitable, more than likely, or generally more predictable then when originally expected or presented. Hindsight bias essentially operates as a means through which people project new knowledge—outcomes—into the previous situation, without any awareness that the perception of the past has been tainted by revisionist information.[17]

Hindsight bias might reinforce premature or unwarranted focus on an innocent suspect in several ways. First, once a suspect becomes the focus of an investigation or prosecution—that is, once police or prosecutors arrive at an outcome in their own quest to determine who they believe is guilty—the hindsight bias would suggest that, upon reflection, the suspect would appear to have been the inevitable and likely suspect from the beginning. Moreover, events supporting a given outcome are typically better remembered than events that do not support that outcome. Hence, once police and prosecutors conclude that a particular person is guilty, not only might they overestimate the degree to which that suspect appeared guilty from the beginning, but they will likely best remember those facts that are incriminating (thereby reinforcing their commitment to focus on that person as the culprit).[18] 

A “reiteration effect” is also linked to hindsight bias. Studies have established that confidence in the truth of an assertion or testimony increases naturally as the assertion is repeated (and increases exponentially with increased reassertion). This increase in confidence from repetition is independent of the truth or falsity of the original statement. Accordingly, the longer that police and prosecutors (and witnesses) live with a conclusion of guilt, repeating the conclusion and bases for those conclusions, the conclusions becomes more entrenched.  Simultaneously, the more obvious it will appear that all evidence pointed towards that conclusion all along from the very beginning.  As a result, this reiteration effect makes it increasingly difficult for police and prosecutors to consider alternative perpetrators or theories of a crime, and the greater significance this consideration must hold for those involved with a post-conviction review process.[19]  

   D.        Outcome Bias and Expectancy Bias

Outcome bias describes the process whereby people interject new knowledge (or new plausible outcomes) into past conclusions when in fact the outcome information was influenced by their foregone perception of the past. 

Outcome bias differs slightly from hindsight bias in that outcome bias does not refer to the effect of outcome information on the judged probability of an outcome, but to its effect on the evaluations of decision quality.  In other words, outcome bias does not reflect a judgment as to how likely an event appears to have been, rather the hindsight reflect upon whether a decision was good or bad, correct or incorrect. When people are affected by this bias there rarely any notion or awareness of its occurrence.[20] 

Even when people understand that outcome bias is inappropriate, it is difficult to overcome; as with hindsight bias, people tend to show an outcome bias even when they think they should not, and . . . even though they think they do not.[21]

Hindsight bias and outcome bias, together, should be expected to have an affirmance-biasing effect in the post-conviction review process because the conviction conclusion will appear, always in hindsight, to have been both inevitable and correct in judgment.  The simple data to support that conclusion is how extremely rare are reversals in criminal cases.  Even when a court finds error, it is frequently forgiven under the “harmless error doctrine”.[22] These is virtually no data on the inverse review of court finality because criminal appellate law almost always focuses on challenges brought by the convicted defendant. The double jeopardy clause prohibits most prosecutorial appeals of acquittals.  

An expectancy bias is when people are being led by circumstances into a pre-expected fact or condition.  This is especially true when facts or conditions fall into informationally ambiguous situations.  This is a foundational tendency and lead to error biased in the direction of the expectation[23]

 IV.        A Call for Transparency

A call for transparency is an obvious important step towards sensitizing police, prosecutors, judges and even defense attorneys to these problems.  To help understand pitfalls inherent in the system’s process is a first step towards understanding the consequences, nature, and effects of these underlying biases and institutional pressures.[24] Unfortunately, research suggests that merely informing people about cognitive bias, tunnel vision and other hindsight biases, or even urging a person to overcome such biases, is somehow ineffective.[25]  

To the extent that training and new procedures are inadequate to overcome the powerful forces that produce tunnel vision, an additional reform is necessary. Given that police and prosecutors, because they are human, cannot be expected to recognize and correct for all of their natural biases, the system must find a way to give sufficient case information to those who have different incentives and different natural biases. In the end, greater transparency at all stages of the criminal process is the most powerful way to counter tunnel vision.[26]

Providing full investigative information to a defense team (or other interested parties to the litigation) improves the likelihood of the one party best situated for evaluating the evidence free from guilt-confirming biases to being presented with that role.  (Although, defense counsel are also subjected to condition to believe that the defendant clients are guilty, they at least are subject to considerable countervailing pressures, not to mention ethical obligations, which make them better situated than police or prosecutors to approach a case with an alternative perspective.[27]) Sharing all information with true transparency, with all actors who may have an incentive to look outside the tunnel, can only work towards bringing about greater faith in the finality of the conviction.[28]

Transparency helps to counter cognitive hindsight tunnel vision biases in another important way by helping to modify the effects of biases on sole decision-makers. Psychological research has shown that when people feel publicly accountable for decisions, they exhibit less bias in their hypothesis testing strategies.[29] 

With conviction integrity units the more that investigations are conducted in open and observable ways, the more likely police and prosecutors are to resist biasing pressures and tendencies. Understandably there is certainly room for secrecy or confidentiality in police work or prosecutions such as sensitive information that could jeopardize witness safety cannot be made public.  However, with post-conviction claims of actual innocence those shields of secrecy should be called upon for only the most extreme circumstances seeing as how parties involved are already privy to the witnesses and evidence being reviewed.

Overwhelming research suggests that, whenever, wherever, and however possible, transparency in the criminal justice system should be an objective.  Such actions serve to enhances reliability as well as public trust and confidence in the system to which we are all, directly or indirectly, connected.[30]     

   V.        Conclusion

Eliminating the psychological bias of tunnel vision in all these various manifestations is a most intractable problems underlying wrongful convictions, especially wrongful convictions of the innocent. With so many causes deeply rooted in our psyches, our culture, and our institutions, and because it has such multivariate expressions, a simple solution eludes us all.  

Reforms can begin along several fronts. First, to the extent that existing legal rules enforce tunnel vision, doctrinal reform is an obvious place to begin. Second, education and training must be an important part of the solution to help system actors understand the nature of the problem and attempt to overcome the cognitive biases and institutional pressures that produce tunnel vision. Third, to the extent that tunnel vision is produced by flawed evidence collection and investigation techniques and procedures, those techniques and procedures should be reexamined. Fourth, police and prosecutors can adopt a variety of management and supervision practices to reduce the risk that tunnel vision will lead to wrongful arrest, prosecution, and conviction. Fifth, to the extent that the cognitive biases and institutional pressures are simply too powerful to overcome from within, greater transparency throughout the criminal justice system offers a way to provide both incentives for police and prosecutors to overcome tunnel vision, and, more importantly, the necessary information to those who already have an incentive to see outside the tunnel so that they can pursue alternative theories about a case. Finally, we propose a few major reforms to the police and prosecution institutions to minimize the effects of tunnel vision.[31]

This is something which no one person, or even one group of people can solve, and instead requires diligence, commitment, often attempts which lead to failures, false starts, and continual efforts.  Even when the possibly of hope for a solution recedes from us, hope should not fail.  Instead, the efforts and attempts are perhaps the best solution we can put forth collectively, defying simple solutions.

[additional summations and conclusions]