Why Ask a Suspect for Precise Details That Can Be Checked Later?

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

When investigators ask a suspect for precise details that can be checked later, they are using a principle that deception researchers call the verifiability approach. The logic starts from a dilemma that liars face: they want to sound detailed and convincing, but they also want to avoid saying anything that could be proven false. Research by Galit Nahari, Aldert Vrij and Ronald Fisher has found that truth tellers tend to include more details that an investigator could independently verify, such as naming a specific person they were with, a shop they visited or a transaction that would leave a record. Liars, by contrast, tend to fill their accounts with details that sound rich but cannot easily be checked. The technique does not catch liars automatically. It gives the investigator a framework for evaluating what kind of detail a person is offering and why.

Key takeaways

The verifiability approach distinguishes between details that can be checked (verifiable) and details that cannot (unverifiable).
Truth tellers provide more verifiable details and a higher ratio of verifiable to unverifiable details than liars.
Liars face a strategic dilemma: they want to appear detailed but avoid offering checkable information.
A 2014 study correctly classified 79% of participants based on the frequency of verifiable details alone.
The approach improves when interviewees are told their details will be checked, because truth tellers respond by adding more verifiable information while liars do not.

What is the verifiability approach?

The verifiability approach was developed by Nahari, Vrij and Fisher and first published in Legal and Criminological Psychology in 2014. It starts from a well-established finding in deception research: liars strategically manage the level of detail in their accounts. Earlier research, including DePaulo and colleagues' 2003 meta-analysis, found that liars tend to be somewhat less forthcoming than truth tellers. But the verifiability approach goes further by classifying the type of detail rather than just the amount.

A verifiable detail is one that an investigator could, in principle, check. Examples include:

Naming a specific person who was present ("I was with my colleague Sarah")
Referring to a recorded transaction ("I paid by card at the petrol station")
Mentioning a location with CCTV or witnesses ("I walked through the train station concourse")

An unverifiable detail is one that sounds specific but cannot easily be confirmed or denied. Examples include:

Internal states ("I was feeling anxious")
Actions without witnesses ("I sat alone in the park")
Vague time references ("I was there for a while")

The approach predicts that truth tellers will naturally include more verifiable details because their accounts are drawn from real events that involved real people, real places and real records. Liars will tend to avoid verifiable details because each one creates a potential point of failure.

What does the research show?

The 2014 founding study

Nahari, Vrij and Fisher's 2014 study asked mock criminals (liars) and innocent participants (truth tellers) to provide written statements about their activities during a specified time period. The researchers then coded each statement for verifiable and unverifiable details.

Truth tellers included significantly more verifiable details than liars. The ratio of verifiable to unverifiable details was also higher for truth tellers. Based on the frequency of verifiable details alone, 79% of participants were correctly classified. Based on the ratio, 71% were correctly classified.

What happens when you tell people their details will be checked?

A follow-up study by Nahari, Vrij and Fisher examined whether informing interviewees that the verifiability of their statements would be checked affected the results. It did, but in an asymmetric way: truth tellers who were informed provided significantly more verifiable details, while liars did not increase their verifiable detail count. This widened the gap between the two groups and improved classification accuracy.

This is an unusual property for a deception detection technique. Many methods lose effectiveness when the interviewee knows what the interviewer is looking for, because both truth tellers and liars can adjust their behaviour. The verifiability approach appears to be less vulnerable to this problem because only truth tellers have genuine verifiable experiences to draw on.

Meta-analytic evidence

A meta-analysis by Vrij and colleagues examined the accumulated evidence across multiple studies. It confirmed that truth tellers consistently provided more verifiable details and a higher proportion of verifiable details than liars. The effect was larger when the statement concerned an alibi, where the truth teller would naturally have been doing something involving other people and leaving traces. The effect was somewhat smaller when participants were given a financial incentive to appear credible, suggesting that motivated liars may work harder to include checkable details.

How do investigators use this in practice?

The verifiability approach is not a mechanical test. An investigator does not simply count verifiable details and declare a threshold. Instead, the approach suggests a framework for evaluating a statement:

Ask for a detailed account. Give the interviewee time and encouragement to provide a full narrative.
Note what kind of details they offer. Are they naming people, places, times and transactions that could be checked? Or are they providing vivid but uncheckable descriptions?
Follow up on verifiable claims. The approach works best when the investigator actually checks the details offered. A truth teller's account should hold up. A liar's account may start to unravel.

This connects to the broader principle of corroborating evidence: statements are stronger when they can be independently confirmed.

What are the limits?

Some truthful accounts lack verifiable details. A person who was genuinely alone, without their phone, in a location without cameras, may have very few verifiable details to offer. The absence of checkable information does not prove deception. Why might an innocent person refuse to answer questions? discusses related issues.
Motivated liars can include false verifiable details. A liar who is willing to name specific people or places, knowing those claims will be checked and found false, trades one risk for another. The approach assumes that liars prefer to avoid checkable claims, but some may choose to bluff.
Classification is not certain. The 79% accuracy rate in the founding study means roughly one in five people would be misclassified. Like all deception detection methods, the verifiability approach improves the odds but does not eliminate error.
Cultural and contextual factors matter. People from different backgrounds may naturally include different types and amounts of detail. Research has primarily been conducted in Western laboratory settings, and the findings may not generalise equally to all populations.

How does this relate to other cognitive techniques?

The verifiability approach is part of a family of interview strategies that exploit the cognitive and strategic differences between truth tellers and liars. Others include asking unexpected questions, reverse order recall and asking suspects to demonstrate what happened. Each targets a different weakness in fabricated accounts: unexpected questions test preparedness, reverse order tests rehearsal, demonstration tests spatial memory and verifiable details test willingness to offer checkable information.

Researchers generally recommend combining approaches. The strategic use of evidence technique, for example, shares the verifiability approach's emphasis on checking claims against independent information.

How does this relate to Murder Book?

Murder Book is an upcoming narrative interrogation game from Gungrounds, an independent studio in Zagreb, Croatia. The game's press kit names Fabrication among the interrogation behaviours players examine. Development screenshots show an evidence board that links suspect statements to physical evidence, allowing the player to test whether claims hold up.

The verifiability approach maps closely to this mechanic. In the research, investigators look at whether a suspect offers details that can be checked. In Murder Book, players compare what a suspect says against the evidence they have gathered, looking for claims that are either supported or contradicted by the available information. The game treats contradictions as grounds for further questioning, not as automatic proof, which reflects the research finding that the verifiability approach improves detection but does not guarantee it.

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