Case File 306 · Investigation Psychology

Confirmation Bias vs Tunnel Vision: What's the Difference?

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

Confirmation bias and tunnel vision are related but distinct concepts. Confirmation bias is a general cognitive tendency: people seek, notice and interpret information in ways that support what they already believe. Tunnel vision is what happens when confirmation bias and other cognitive shortcuts operate within a criminal investigation, causing investigators, prosecutors and other participants to lock onto a single suspect or theory and filter all evidence through that lens. In short, confirmation bias is one of the main psychological mechanisms that drives tunnel vision, but tunnel vision is a broader pattern that also involves institutional pressures, role-based incentives and the compounding of errors across the justice system.

Key takeaways

Confirmation bias is a general cognitive phenomenon; tunnel vision is its expression within the criminal justice system.
Tunnel vision includes confirmation bias but also involves anchoring, belief perseverance, institutional pressure and role effects.
Both can operate unconsciously, without any intent to be unfair.
Research links both to wrongful convictions and flawed forensic analysis.
Addressing tunnel vision requires systemic safeguards, not just individual awareness.

What is confirmation bias?

Confirmation bias is the tendency to favour information that supports an existing belief while giving less weight to information that contradicts it. Raymond Nickerson's 1998 review in Review of General Psychology called it "a ubiquitous phenomenon in many guises" and documented it across more than two hundred studies. He defined it as "the seeking or interpreting of evidence in ways that are partial to existing beliefs, expectations, or a hypothesis in hand."

Confirmation bias affects everyone. It operates in everyday decisions, scientific reasoning, medical diagnosis and criminal investigation. It is not a sign of incompetence or dishonesty; it is a feature of normal human cognition. The bias can appear in several forms:

Selective search: looking for evidence that confirms a hypothesis rather than evidence that could disprove it.
Biased interpretation: reading ambiguous evidence as supporting a preferred theory when it could equally support an alternative.
Selective recall: remembering information that fits the hypothesis more easily than information that does not.

What is tunnel vision?

Tunnel vision, as used in the criminal justice context, describes a broader pattern. Findley and Scott (2006) defined it in the Wisconsin Law Review as the product of common heuristics and logical fallacies that lead criminal justice actors to "focus on a particular conclusion and then filter all evidence in a case through the lens provided by that conclusion."

The Canadian Public Prosecution Service describes tunnel vision as 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."

While confirmation bias is one cognitive process, tunnel vision draws on several:

Anchoring bias: an early piece of evidence, such as an eyewitness identification, anchors the investigation to a particular suspect.
Belief perseverance: once committed to a theory, investigators may cling to it even after its original basis has weakened.
Role effects: prosecutors are tasked with building a case; this structural role can reinforce one-sided evidence gathering even when individual prosecutors act in good faith.
Institutional pressure: deadlines, public attention and the expectation of arrests can push an investigation to commit to a theory before the evidence justifies it.

How are they connected?

Legal scholars typically treat confirmation bias as one element within tunnel vision. The Canadian guidance on tunnel vision describes confirmation bias as "a powerful psychological process" that causes a person to "unconsciously prefer information that supports a conclusion that they have already settled on and to disregard or be overly sceptical about information that contradicts that conclusion." In this framing, confirmation bias is the engine; tunnel vision is the vehicle it drives.

Kassin, Dror and Kukucka (2013) described a related concept, forensic confirmation bias, in which contextual case information corrupts the judgments of forensic examiners. They showed that the bias flows through the justice system: a confession can influence how police investigate, how forensic analysts evaluate evidence and how witnesses remember events. Each biased step reinforces the next, creating a self-reinforcing cycle that is difficult to interrupt.

What does the research say about their impact?

Both confirmation bias and tunnel vision have been linked to wrongful convictions. Findley and Scott (2006) argued that tunnel vision is not one isolated error but a theme connecting nearly every case of wrongful conviction. They noted that mistaken eyewitness identification, false confessions, forensic error and other recognised causes of wrongful conviction are often connected by the same underlying pattern of narrowed focus.

Dror, Charlton and Péron (2006) showed experimentally that fingerprint examiners changed their conclusions when given different contextual information about the same prints. The evidence itself was identical; only the information surrounding it had changed. This finding illustrates how confirmation bias can operate at the forensic level, feeding into the broader tunnel vision pattern.

Research on the Ford Heights Four case in Chicago found that police and prosecutors maintained a tunnel vision approach that prevented them from following leads pointing to the actual perpetrators. The wrongly accused spent years imprisoned before being exonerated.

How can they be addressed?

Because tunnel vision involves more than just confirmation bias, addressing it requires more than awareness training alone:

Generate competing hypotheses: formally asking what other explanations fit the evidence helps counteract the tendency to settle on one theory.
Blind forensic analysis: Kassin, Dror and Kukucka (2013) recommended that forensic examiners should evaluate evidence without knowing confessions, suspect identities or other potentially biasing case details.
Devil's advocate review: assigning someone to argue against the prevailing theory can surface overlooked evidence.
Structured decision-making: checklists and formal review stages can catch one-sided reasoning before it becomes entrenched.
Post-conviction review: studying cases where errors occurred helps institutions learn from their failures.

Nickerson (1998) noted that simply telling people about confirmation bias does not eliminate it. The bias is robust because it operates automatically. Systemic safeguards matter more than good intentions.

How does Murder Book explore these ideas?

Murder Book: The Art of Interrogation is an upcoming narrative interrogation game from Gungrounds, an independent studio in Zagreb, Croatia. Players examine suspects' stories for behavioural changes, narrative gaps and contradictions. Development screenshots show a technique menu including options such as Confrontation and Baiting, and an evidence board that links conflicting statements. The game's branching case map, with multiple endings, means that locking onto a single reading of the evidence can lead to the wrong conclusion.

The game does not tell the player who is guilty. It presents behaviour and statements that must be weighed, not taken at face value. This design reflects the lesson that both confirmation bias and tunnel vision teach: the danger is not in having a theory, but in refusing to test it.

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