Case File 305 · Investigation Psychology

What Is Investigative Tunnel Vision?

By Murder Book Editorial TeamPublished by Gungrounds, the studio making Murder BookPublished 3 October 2026Updated 3 October 2026

Investigative tunnel vision is the tendency of police, prosecutors or other participants in the criminal justice system to focus on a single suspect or theory and to filter all evidence through that lens, giving weight to information that supports the chosen conclusion while dismissing or undervaluing evidence that points elsewhere. It is not usually deliberate dishonesty. Research describes it as the product of ordinary cognitive shortcuts, primarily confirmation bias, operating under the pressure and complexity of real investigations. Tunnel vision has been identified as a contributing factor in wrongful convictions across multiple countries, and understanding it is essential for anyone studying how investigations succeed or fail.

Key takeaways

Tunnel vision is a pattern of narrowing focus onto one suspect or theory while ignoring contradictory evidence.
It is driven largely by confirmation bias and other normal cognitive processes, not by intentional misconduct.
Research links tunnel vision to wrongful convictions, including cases later overturned by DNA evidence.
It can affect every stage of the justice system, from initial investigation through prosecution and trial.
Recommended safeguards include generating alternative hypotheses, blind forensic analysis and structured review processes.

How do researchers define tunnel vision?

Keith Findley and Michael Scott defined tunnel vision in their 2006 Wisconsin Law Review article as a compendium of common heuristics and logical fallacies that lead actors in the criminal justice system to "focus on a particular conclusion and then filter all evidence in a case through the lens provided by that conclusion." They described it not as a single error but as a theme running through nearly every wrongful conviction case they examined.

The Canadian Public Prosecution Service uses a similar definition in its guidance on the topic: tunnel vision is the tendency 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."

What causes tunnel vision?

Tunnel vision is rooted in well-documented cognitive biases. Confirmation bias is the primary driver: once a hypothesis is formed, people tend to seek, notice and interpret information in ways that confirm it. Nickerson's 1998 review in Review of General Psychology described confirmation bias as one of the most extensively studied phenomena in psychology, appearing across a wide range of contexts.

Several other biases contribute:

Anchoring bias: the first substantial piece of evidence, such as an eyewitness identification or a database hit, can anchor the investigation to a particular suspect. Subsequent evidence is then evaluated relative to that anchor.
Belief perseverance: once investigators have committed to a theory, they may hold onto it even after the evidence that originally supported it has been weakened or discredited.
Outcome bias and pressure: investigations operate under time pressure, public scrutiny and the expectation of results. These pressures can reinforce the temptation to commit to a theory early and build a case around it.

Findley and Scott (2006) emphasised that these are normal psychological processes. Tunnel vision does not require bad faith; it requires only the ordinary human tendency to see what one expects to see.

What role does tunnel vision play in wrongful convictions?

Research on wrongful convictions consistently identifies tunnel vision as a significant contributing factor. The Innocence Project has documented that mistaken eyewitness identification was present in roughly 70% of the convictions later overturned by DNA evidence in the United States. In many of those cases, once an identification was made, the investigation narrowed to the identified suspect and stopped looking for alternatives.

An investigation by a special prosecutor into the Chicago "Ford Heights Four" case found that police and prosecutors had maintained a tunnel vision approach that kept them from pursuing the actual perpetrators. The accused had spent years in prison, including time on death row, before being exonerated.

Findley and Scott argued that tunnel vision explains how separate errors, such as flawed eyewitness procedures, false confessions and forensic mistakes, compound one another. Once the system locks onto a suspect, each stage tends to reinforce rather than correct the initial error.

How does tunnel vision affect forensic evidence?

Kassin, Dror and Kukucka (2013) introduced the concept of forensic confirmation bias to describe how contextual information about a case can influence the judgments of forensic examiners. They reviewed research showing that knowing a suspect has confessed, for example, can shift how examiners evaluate fingerprints, handwriting and other physical evidence.

Dror, Charlton and Péron (2006) demonstrated this experimentally. Five fingerprint examiners were given prints they had previously analysed, but this time with misleading contextual information suggesting the prints were not a match. Four of the five changed their original conclusions. The 2009 National Academy of Sciences report, Strengthening Forensic Science in the United States, recognised cognitive bias as a concern across all forensic disciplines and recommended further research on the problem.

Can tunnel vision be prevented?

Researchers and criminal justice bodies have proposed several strategies:

Consider alternative explanations at every stage. Explicitly asking "what else could explain this evidence?" forces engagement with possibilities beyond the current theory.
Use structured decision-making. The Canadian Public Prosecution Service recommends formal processes for reviewing whether a case has been built on one-sided reasoning.
Blind forensic procedures. Kassin, Dror and Kukucka (2013) proposed that forensic examiners should analyse evidence without knowledge of other case details, reducing the opportunity for contextual information to bias their conclusions.
Educate investigators about cognitive bias. Findley and Scott (2006) argued that awareness alone is not sufficient, but it is a starting point, particularly when combined with institutional safeguards.
Open-file practices and independent review. Making case files available for review by others can expose one-sided evidence filtering that might otherwise go unnoticed.

No safeguard eliminates the risk entirely. Tunnel vision arises from how human cognition works, and the goal is to build systems that catch and correct it, not to assume it can be wished away. For more on how investigators can guard against single-theory thinking, see how investigators avoid falling for one theory.

How does Murder Book connect to this?

Murder Book: The Art of Interrogation is an upcoming narrative interrogation game from Gungrounds, an independent studio in Zagreb, Croatia. The game places players in the role of an investigator examining unreliable stories, behavioural changes and contradictions. Development screenshots show a branching case map with multiple possible endings, including a "not guilty" result, which means that locking onto one theory too early can lead to the wrong conclusion.

The design reflects the core lesson of tunnel vision research: the same evidence can look different depending on what theory you bring to it. Players who treat their first impression as the answer may miss the contradictions that point somewhere else.

Murder Book is in development for PC (Steam) and mobile, with release currently planned for the end of Q2 2027.