Case File 287 · Investigation Psychology

Why Should Investigators Consider Alternative Explanations?

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

Investigators should consider alternative explanations because the human mind is wired to favour the first plausible account it settles on, and that tendency leads to mistakes. Research on wrongful convictions has consistently identified tunnel vision, the narrow focus on a single suspect or theory to the exclusion of other possibilities, as a leading contributor to investigative failure. Considering alternative explanations is not a sign of indecision; it is a disciplined practice that protects against cognitive bias, reduces the risk of wrongful conviction, and increases the chance of identifying the actual perpetrator.

Key takeaways

Tunnel vision, the tendency to lock onto one theory and filter evidence through it, has been identified as a central factor in wrongful convictions.
Findley and Scott (2006) found that investigators, prosecutors and even defence lawyers can become so focused on a conclusion that they ignore evidence pointing away from guilt.
O'Brien (2009) showed experimentally that asking people to generate reasons why their initial suspect might be innocent significantly reduced confirmation bias.
Rossmo (2009) recommends maintaining multiple hypotheses and bringing in fresh perspectives to challenge established thinking.
Considering alternative explanations is a safeguard, not a weakness. It strengthens investigations by ensuring conclusions are driven by evidence rather than assumption.

What happens when investigators do not consider alternatives?

The consequences of failing to consider alternative explanations are well documented. Findley and Scott (2006), writing in the Wisconsin Law Review, examined dozens of wrongful conviction cases and found that tunnel vision was a recurring theme. They described it as a natural human tendency with "particularly pernicious effects in the criminal justice system."

Their analysis showed how investigators, once they settle on a suspect, begin to "select and filter the evidence that will build a case for conviction, while ignoring or suppressing evidence that points away from guilt." This is not necessarily deliberate misconduct. It reflects the way human cognition works: once a belief takes hold, people unconsciously seek information that confirms it and discount information that contradicts it. Confirmation bias and tunnel vision are closely related but distinct problems.

The real-world cost is significant. When an investigation commits to the wrong theory, the actual perpetrator may remain free, evidence degrades over time, and innocent people may spend years or decades in prison. DNA exoneration cases have repeatedly revealed investigations where viable alternative suspects or explanations were never pursued.

Why is it so hard to consider alternatives?

Several well-documented cognitive biases make it difficult for investigators to step back and consider other possibilities:

Confirmation bias leads people to seek, notice and remember information that supports their existing belief while overlooking contradictory evidence. In an investigation, this means that once a detective suspects someone, every ambiguous piece of evidence tends to be read as confirmation.

Belief perseverance means that even when the original basis for a belief is undermined, the belief itself can persist. What Is Belief Perseverance? explains how this works: if the key witness recants, the investigator may find reasons to distrust the recantation rather than reconsidering the theory.

Anchoring bias describes how the first piece of information encountered disproportionately shapes later judgments. What Is Anchoring Bias in an Investigation? explores how an early tip or a first impression at a crime scene can anchor the entire direction of a case.

Groupthink occurs when a team of investigators reinforces each other's assumptions, making dissent uncomfortable and alternative theories unwelcome. Rossmo (2009) identifies this as an organisational trap that compounds individual cognitive biases.

What does the research say about debiasing?

O'Brien (2009), publishing in Psychology, Public Policy, and Law, conducted experiments that directly tested whether generating alternative explanations could reduce confirmation bias in an investigative context.

Participants reviewed a mock police file containing weak circumstantial evidence pointing to one suspect. A second, stronger suspect emerged later in the file. Participants who had formed an early hypothesis about the first suspect tended to stick with that hypothesis even after encountering the stronger evidence against the second suspect. However, when participants in a second experiment were asked to generate reasons why their initial suspect might be innocent, the confirmation bias was significantly reduced.

This finding has practical implications. It suggests that a simple, structured exercise, asking "Why might this person not be guilty?" or "What would the evidence look like if someone else did this?", can meaningfully counteract the pull of an established theory.

What practical steps help investigators consider alternatives?

Based on the research literature, several strategies have been recommended:

Maintain a list of alternative hypotheses. From early in the investigation, write down at least two or three plausible explanations for the evidence. Update the list as new facts emerge. See How Do Investigators Test Competing Hypotheses? for a structured approach.

Assign a devil's advocate. Rossmo (2009) recommends bringing someone into the investigation who is specifically tasked with challenging the prevailing theory. This person should be empowered to ask uncomfortable questions without facing social pressure from the team.

Use a case review. Periodically have someone who was not involved in forming the original theory review the evidence independently. A fresh perspective is less susceptible to the biases that accumulate during an investigation.

Ask what evidence would disprove the theory. This is the principle behind disconfirming evidence. If the answer is "nothing could change my mind," the investigation has a problem.

Document reasoning. Writing down why a particular theory was adopted and what evidence supports or contradicts it creates accountability and makes it easier to revisit assumptions later.

Separate evidence gathering from theory building. The information-gathering approach to interviewing, used in frameworks like the PEACE model, aims to collect a complete account before testing it against a theory. This reduces the risk that the interview itself is shaped by a predetermined conclusion.

How does considering alternatives affect the quality of evidence?

When investigators seriously consider alternative explanations, they tend to gather a wider range of evidence. Instead of focusing only on evidence that implicates the primary suspect, they may pursue leads that could implicate someone else or that could exonerate the suspect entirely.

This broader evidence base benefits the investigation regardless of where it leads. If the original suspect is guilty, the additional evidence strengthens the case by ruling out alternative explanations a defence attorney might raise. If the original suspect is innocent, the broader search may identify the actual perpetrator before more time and evidence are lost.

Kassin, Bogart and Kerner (2012) showed how a failure to maintain independence can work in the opposite direction: when investigators are committed to one theory, even forensic analysts and witnesses can be influenced by that commitment, producing evidence that appears to corroborate the theory but is not truly independent. Maintaining alternatives is one way to guard against this confession bias effect.

How does this connect to Murder Book?

Murder Book: The Art of Interrogation is an upcoming narrative interrogation game from Gungrounds in which reaching the right conclusion requires weighing what you see and hear rather than accepting the most obvious explanation. Development screenshots show a branching case map with multiple endings, including a "not guilty" result, which means the game acknowledges that the evidence does not always point where it first appears to.

The game's in-game casebook lists behaviours such as Avoidance, Fabrication and Narrative Gaps, but development materials present these as patterns to investigate further, not as proof. Players who jump to a conclusion based on a single behaviour or statement risk reaching the wrong ending. The structure rewards the kind of open-minded evaluation that researchers recommend for real investigations.

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