Case File 304 · Investigation Psychology

Can One Piece of Evidence Support More Than One Theory?

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

Yes, a single piece of evidence can legitimately support more than one theory. A witness placing a suspect near a crime scene, for instance, is consistent with guilt but also with the suspect simply living or working nearby. A fingerprint on a doorknob could mean the person committed a crime inside the building, or that they visited on a different day entirely. In criminal investigation, this ambiguity is not a flaw in the evidence; it is a fundamental feature of how evidence works. Investigators, prosecutors and jurors must weigh each item alongside other evidence rather than treating any single finding as conclusive proof of one explanation. Recognising that evidence can point in more than one direction is one of the strongest safeguards against tunnel vision in investigations.

Key takeaways

Most individual pieces of evidence are consistent with more than one explanation of events.
Treating ambiguous evidence as though it supports only one theory is a recognised source of investigative error.
Confirmation bias can lead investigators to interpret neutral evidence as supporting their existing hypothesis.
Building a strong case requires looking at how multiple pieces of evidence fit together, not reading each item in isolation.
Research on wrongful convictions shows that failures to consider alternative explanations contribute to miscarriages of justice.

Why can evidence fit more than one theory?

Evidence rarely comes with a label explaining exactly what it means. A bloodstain confirms that someone bled; it does not explain when, how or why. A phone record shows a call was made; it does not reveal the conversation or its purpose. Researchers in forensic science and legal reasoning describe this as the problem of underdetermination: the available evidence is compatible with multiple accounts of what happened.

The Canadian Public Prosecution Service's guidance on tunnel vision notes that evidence which appears to build a case against one suspect may also be consistent with innocence or with the involvement of another person entirely. Findley and Scott, in their 2006 Wisconsin Law Review article on tunnel vision in criminal cases, describe how investigators and prosecutors can unconsciously filter evidence through the lens of a conclusion they have already reached, overlooking the fact that the same evidence could support a different theory.

How does confirmation bias affect the way evidence is read?

Once an investigator forms a working theory, confirmation bias can shape how every subsequent piece of evidence is interpreted. Raymond Nickerson's 1998 review in the Review of General Psychology called confirmation bias "a ubiquitous phenomenon in many guises" and documented how people tend to seek, notice and remember information that supports what they already believe while giving less weight to information that contradicts it.

In a criminal investigation, this means that ambiguous evidence is more likely to be read as supporting the current theory than as challenging it. Kassin, Dror and Kukucka (2013) described this process as forensic confirmation bias, showing that contextual information, such as knowing a suspect has confessed, can influence how forensic examiners evaluate physical evidence. Their review found that confessions and other case information can corrupt expert judgments across multiple forensic domains.

Dror, Charlton and Péron (2006) demonstrated this experimentally with fingerprint examiners. When examiners were given misleading contextual information about a case, four out of five changed their prior identification decisions. The evidence itself had not changed; only the context in which it was evaluated had shifted.

What happens when investigators treat evidence as supporting only one theory?

When ambiguous evidence is locked to a single interpretation, the investigation narrows. Investigative tunnel vision describes this narrowing: the tendency to focus on one suspect or one explanation and to dismiss or undervalue anything that does not fit. Findley and Scott (2006) argued that tunnel vision is not one isolated error but a theme running through almost every wrongful conviction they studied.

The consequences can be severe. The Innocence Project has documented that mistaken eyewitness identification contributed to roughly 70% of the wrongful convictions later overturned by DNA evidence in the United States. In many of those cases, identification evidence that was consistent with more than one person was treated as though it could only point to the defendant.

How should investigators handle evidence that fits multiple explanations?

Researchers and professional guidelines suggest several practices:

Generate competing hypotheses early. Rather than testing only whether the evidence fits one theory, investigators can ask what other theories the same evidence would also support. The Canadian Public Prosecution Service recommends that prosecutors actively consider alternative explanations throughout a case.
Separate evidence from context where possible. Kassin, Dror and Kukucka (2013) proposed that forensic examiners should evaluate physical evidence without knowing the suspect's confession status or other potentially biasing case information.
Seek disconfirming evidence. Nickerson (1998) noted that actively looking for evidence that would contradict a hypothesis is one of the most effective defences against confirmation bias. For more on this, see why disconfirming evidence matters.
Document alternative interpretations. Writing down how a piece of evidence could support a different theory forces the investigator to engage with that possibility rather than dismiss it.

What does this mean for evaluating a case?

The strength of a case does not come from any single piece of evidence; it comes from the pattern formed when multiple independent pieces converge on the same explanation. Circumstantial evidence, by definition, requires an inference, and the same circumstance can often support more than one inference. Corroborating evidence from independent sources is what separates a well-supported theory from one that merely fits the available facts.

Understanding this principle does not make evidence useless. It makes the process of weighing evidence more careful and more honest. A single item may be ambiguous; a pattern of items pointing the same way is much harder to explain away.

How does Murder Book explore this idea?

Murder Book: The Art of Interrogation is an upcoming narrative interrogation game from Gungrounds, an independent studio in Zagreb, Croatia. Development screenshots show an evidence board that links statements from suspects, such as "I NEVER met her!" connected to a fabricated description of a gun. Players examine these connections and decide how to interpret them, knowing that a statement might be a lie, a genuine mistake or a truthful account viewed out of context.

The game's branching case structure means that the same piece of evidence can lead to different conclusions depending on how the player weighs it alongside other findings. This mirrors the real investigative challenge: evidence does not come with a single correct reading, and the player must decide which interpretation the full picture supports.

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