Why Don't Investigators Reveal All Their Evidence Immediately?

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

Investigators often delay revealing what they know because early disclosure lets a suspect tailor their account to fit the evidence. By holding back key facts and asking open questions first, an interviewer can compare what the suspect says voluntarily against what the evidence actually shows. If the suspect's free account contradicts undisclosed evidence, that inconsistency is informative. If it aligns, the interviewer learns something too. The approach is not about tricking people; it is about creating conditions in which truthful and deceptive accounts are more likely to differ. This strategy is central to a framework researchers call the Strategic Use of Evidence (SUE), developed by Pär Anders Granhag and Maria Hartwig, which has become one of the most studied interview techniques in deception research.

Key takeaways

Revealing all evidence at the start of an interview lets a deceptive suspect adjust their story to match, reducing the chance of catching inconsistencies.
The Strategic Use of Evidence (SUE) framework recommends gathering a free account before introducing evidence, so the interviewer can compare the two.
Research finds that liars are more likely to produce statements that contradict withheld evidence, while truth tellers tend to be consistent with it.
Early evidence disclosure is associated with accusatorial methods, while late disclosure is a hallmark of information-gathering approaches.
Withholding evidence is not about deception by the interviewer; it is about giving the suspect's own words room to confirm or contradict the facts.

What is the Strategic Use of Evidence?

The Strategic Use of Evidence (SUE) framework was developed by researchers Pär Anders Granhag and Maria Hartwig at the University of Gothenburg. It starts from a simple observation: guilty suspects and innocent suspects tend to behave differently when they do not know what evidence the interviewer holds.

According to Hartwig, Granhag, Strömwall and Kronkvist (2006), guilty suspects are more likely to use avoidance strategies, steering their account away from incriminating topics, or denial strategies, directly contradicting the evidence. Innocent suspects, by contrast, are more likely to give forthcoming accounts that happen to be consistent with the evidence, because they are simply reporting what they experienced.

The SUE technique exploits this difference by structuring the interview in stages:

Ask open, non-leading questions to gather the suspect's free narrative.
Note which topics the suspect avoids, denies or contradicts relative to the evidence.
Introduce the evidence gradually, asking the suspect to explain specific discrepancies.

When the interviewer reveals all evidence at the outset, a deceptive suspect can construct a story around it. When evidence is held back, the suspect must guess what the interviewer knows, and liars frequently guess wrong.

Does withholding evidence actually help detect deception?

Several studies have tested whether the timing of evidence disclosure affects an interviewer's ability to distinguish truth tellers from liars.

Hartwig, Granhag, Strömwall and Vrij (2005) conducted an experiment in which some participants committed a mock crime and others did not. Interviewers who were trained to use evidence strategically, presenting it late rather than early, achieved significantly higher accuracy in distinguishing liars from truth tellers compared to interviewers who presented evidence at the beginning.

A later study by Hartwig, Granhag, Strömwall and Kronkvist (2006) found that trained interviewers using the SUE approach correctly classified about 85% of liars and truth tellers, compared with around 56% for untrained interviewers. The key mechanism was that strategic evidence use produced more statement-evidence inconsistencies from guilty suspects and more consistencies from innocent ones.

Jordan, Hartwig, Wallace, Dawson and Xhihani (2012) extended this work by examining how suspects adapt their strategies when they have varying amounts of information about what evidence the interviewer holds. They found that suspects who knew less about the available evidence were more likely to make statements that conflicted with it.

These findings align with the broader observation from information-gathering interviews that non-confrontational, open-ended questioning tends to produce more diagnostic information than accusatorial questioning.

How does this differ from an accusatorial approach?

In accusatorial methods such as the Reid Technique, the interviewer typically confronts the suspect with evidence early in the process to demonstrate that guilt has already been established. The goal is to persuade the suspect that denial is futile and that cooperating is the best option.

The SUE approach takes the opposite path. Rather than using evidence as a tool of persuasion, it uses evidence as a diagnostic instrument. The interviewer's question is not "how do I get this person to confess?" but "how do I find out whether this person's account is consistent with what I know?"

This distinction matters because accusatorial and information-gathering methods carry different risks. Early evidence disclosure combined with confrontation has been linked to increased false confession risk, particularly among vulnerable populations. Late, strategic disclosure does not carry the same pressure because it does not demand a confession; it simply asks the suspect to explain inconsistencies.

The Mendez Principles on effective interviewing recommend rapport-based, non-coercive techniques and emphasise that effective interviewing is about obtaining accurate and reliable information, not securing admissions.

What does withholding evidence look like in practice?

Consider a case where CCTV footage places a suspect near the scene of a crime at a specific time. An interviewer using early disclosure might say: "We have you on camera at the scene at 9 p.m. What were you doing there?" The suspect now knows the footage exists and can build a cover story around it.

An interviewer using strategic disclosure would instead ask: "Can you tell me everything you did that evening?" If the suspect claims they were elsewhere at 9 p.m., the interviewer now has a clear inconsistency to explore. If the suspect mentions being near the scene, that consistency is also informative.

Granhag and Hartwig (2015) describe this as shifting from a "persuasion" approach to a "diagnostic" approach. The goal is not to catch the suspect off guard or to trap them, but to let the evidence do its work by comparing it against an unconstrained account.

Are there limits to this approach?

Strategic evidence use is not a lie detector. It increases the difference between how truthful and deceptive suspects respond, but it does not eliminate uncertainty. Several important caveats apply:

Innocent suspects can be inconsistent. Memory is imperfect, and an innocent person may misremember times, locations or sequences. Inconsistency with evidence is not proof of deception. Research on eyewitness memory shows how readily honest accounts can contain errors.
Experienced suspects may adapt. Jordan and colleagues (2012) noted that suspects who anticipate strategic questioning may adopt counter-strategies, such as providing partial truths that are harder to check.
The quality of the evidence matters. SUE works best when the interviewer holds evidence that is specific and verifiable. Vague or ambiguous evidence produces less diagnostic comparisons.
Training is essential. The accuracy gains in the research depended on interviewers being trained in the technique. Without training, interviewers tended to disclose evidence early and lost the diagnostic advantage.

Vrij and Granhag (2012) noted that one of the strengths of SUE is that it is theoretically grounded and empirically tested, unlike many traditional interview approaches that rely on untested assumptions about behaviour and deception.

Why is gradual disclosure better than all-at-once?

Granhag, Strömwall, Willén and Hartwig (2013) examined different methods of presenting evidence and found that presenting pieces of evidence one at a time, in a gradual fashion, was more effective than presenting all evidence simultaneously. Gradual disclosure gave liars multiple opportunities to commit to details that could then be checked against subsequent pieces of evidence, producing more detectable inconsistencies.

This incremental approach also reduces the risk of overwhelming or intimidating the interviewee. It keeps the conversation flowing and gives the suspect the opportunity to explain each point, which is valuable regardless of whether they are truthful or deceptive.

How does this connect to Murder Book?

Murder Book: The Art of Interrogation builds its gameplay around exactly this kind of evidence management. Development screenshots show an evidence board where players link statements to physical evidence, and a technique menu that includes options such as Confrontation, Baiting and Demonstration. The game asks players to decide when and how to introduce what they know.

In the research literature, the timing of evidence disclosure is one of the few interview strategies with consistent empirical support for improving accuracy. Murder Book translates that principle into a decision the player makes case by case: reveal a piece of evidence now to pressure a response, or hold it back to see whether the suspect's free account contradicts it. Cases are designed for focused 5–10-minute sessions.

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