The SUE Technique: How Investigators Use Evidence to Catch Lies

The Investigator Who Already Knew

On the afternoon of August 14, 2018, CBI Agent Graham Coder sat across from Chris Watts at the Frederick, Colorado police station and asked a simple question: what had he done that morning before leaving for work? Coder already knew the answer. He had reviewed the neighbor’s Vivint doorbell footage frame by frame. He had watched Watts back his truck into the garage at 5:27 AM and spend several minutes loading objects into the bed. He knew Watts’s claim that Shanann left with the girls at 5:15 AM was a geometric impossibility, because the camera showed no one leaving the front door.

Coder did not mention the footage. Not yet. He asked Watts to walk through the morning again, slowly, in his own words. He asked about the garage. He asked about the truck. He gave Watts every opportunity to either tell the truth or to commit, on the record, to a version of events that the evidence would destroy.

This approach, whether Coder named it as such or not, reflects one of the most significant developments in forensic interview science over the past two decades: the Strategic Use of Evidence technique, known in the research literature as SUE. The principle is deceptively simple. When you already hold a piece of evidence, the decision about when to reveal it becomes the most powerful tool in the room.

The Gothenburg Breakthrough

The SUE technique did not emerge from a police training academy or a federal agency task force. It came from an academic research program at the University of Gothenburg in Sweden, where psychologists Pär Anders Granhag and Maria Hartwig spent the early 2000s studying a problem that had frustrated investigators for decades: humans are terrible at detecting lies.

The research base on this point is unforgiving. Decades of studies, compiled in meta-analyses by Aldert Vrij and others, show that people distinguish truth from deception at rates barely above chance. The average accuracy hovers around 54 percent, only marginally better than a coin flip. Police officers perform no better than civilians. Training in behavioral cue detection, the twitches and gaze aversions and nervous gestures that popular culture associates with lying, produces no reliable improvement.

Granhag and Hartwig recognized that the problem was not with the investigators. The problem was with the paradigm. Traditional approaches to deception detection focused on reading the suspect: watching for signs of stress, anxiety, cognitive load. But these cues are unreliable because truthful suspects also exhibit stress. An innocent person accused of a crime has every reason to be nervous, evasive, or emotionally volatile. The behavioral signals overlap so thoroughly between liars and truth-tellers that no amount of training can make them diagnostically useful at the individual level.

What Granhag and Hartwig proposed was a paradigm shift. Stop trying to read the person. Start managing the information.

Their insight rested on a structural asymmetry that exists in every investigative interview where evidence has been collected. The investigator knows what evidence exists. The suspect does not know what the investigator knows. This information gap, when exploited correctly, forces truthful and deceptive suspects into reliably different behavioral patterns, patterns that can be measured rather than intuited.

Granhag and Hartwig called this the “asymmetric information paradigm,” and the interview protocol they built around it became the SUE technique. The first major publications appeared between 2005 and 2006, and by the end of that decade, SUE had become one of the most actively researched interview frameworks in forensic psychology.

Three Phases: Gathering, Approaching, Disclosing

The SUE technique operates through a structured sequence of three phases, each designed to maximize the diagnostic value of the evidence the investigator holds.

Phase One: The Free Narrative

The interview begins with open-ended questions and no mention of evidence. The investigator asks the suspect to describe, in their own words and at their own pace, what happened. “Tell me everything about your Tuesday.” “Walk me through your evening.” “Describe what you did after you left work.”

The goal of this phase is not to extract a confession. The goal is to obtain a detailed, committed account that the investigator can later compare against the evidence. Every claim the suspect makes, every timeline they offer, every person they mention or fail to mention, becomes a data point.

Crucially, the investigator does not challenge, correct, or confront during this phase. The suspect is given room to talk. If they are lying, they will construct a narrative based on what they think the investigator might know, filling in plausible details while omitting or altering the facts that incriminate them. If they are telling the truth, their account will naturally align with the evidence, because they are simply describing what happened.

The free narrative phase also serves a secondary function. It locks the suspect into a story. Once a person has provided a detailed account on the record, they cannot easily abandon it without signaling that they have been strategically managing information. The commitment itself becomes diagnostic.

Phase Two: Specific Questioning

After the free narrative, the investigator begins asking questions that approach the evidence without revealing it. This is the funneling stage, and it requires preparation. Before the interview, the SUE-trained investigator will have mapped each piece of evidence to a set of questions designed to test whether the suspect’s account is consistent with the known facts.

The questions narrow progressively. A broad question: “Did you see anyone else that evening?” A medium question: “Were you near the park at any point?” A specific question: “Did you walk along Oak Street between 9 and 10 PM?”

Each question gives the suspect another opportunity to either confirm or contradict the evidence. A truthful suspect, describing real events, will tend to provide answers that converge with the facts. A deceptive suspect, constructing a false account, will tend to avoid, omit, or contradict the evidence, often without realizing they are doing so, because they do not know what evidence exists.

The investigator takes careful note of every response during this phase. Not just the content of the answers, but the pattern. Where does the suspect volunteer information? Where do they hedge? Where do they provide specific and verifiable details, and where do they retreat into vagueness?

Phase Three: Strategic Disclosure

Only after the first two phases have been completed does the investigator begin revealing evidence. The timing, order, and framing of each disclosure are deliberate.

The investigator might begin with the weakest or most ambiguous piece of evidence to gauge how the suspect responds. Do they adjust their story immediately? Do they offer an explanation? Do they deny the evidence itself? Each response reveals something about the suspect’s strategy.

As the disclosures escalate in specificity and strength, the suspect’s room to maneuver shrinks. If their free narrative and specific answers have already contradicted the evidence, each new disclosure compounds the inconsistency. The investigator does not need to accuse. The evidence speaks, and the gap between the suspect’s account and the documented facts becomes visible to everyone in the room, including the suspect.

Statement-Evidence Inconsistency: The Diagnostic Marker

The central measurement in the SUE framework is what researchers call Statement-Evidence Inconsistency, or SEI. An SEI occurs whenever a suspect’s statement contradicts, omits, or is otherwise inconsistent with a piece of evidence the investigator holds.

Granhag and Hartwig’s research, replicated across more than two dozen studies, shows that deceptive suspects produce significantly more SEIs than truthful ones. The effect is large and consistent. In controlled experiments where some participants committed a mock crime and others did not, SUE-trained interviewers correctly classified liars and truth-tellers at rates far exceeding the 54 percent baseline that characterizes unaided human judgment.

The reason for this disparity is structural. A truthful person is recalling real events. Their account should, by default, align with whatever physical, documentary, or testimonial evidence exists, because the evidence and the person’s memory describe the same reality. Discrepancies will be minor: imprecise times, slightly different spatial descriptions, the normal noise of human recall.

A deceptive person is constructing a fiction. They must decide what to include, what to omit, and what to fabricate, all without knowing what evidence the investigator possesses. Every decision is a gamble. If they claim they were at home when cell tower data places them near the crime scene, they have produced an SEI. If they fail to mention a meeting that three witnesses have already described, they have produced an SEI. If they provide a timeline that contradicts surveillance footage they didn’t know existed, they have produced an SEI.

The accumulation of SEIs across an interview creates a pattern that is far more reliable than any single behavioral cue. One inconsistency might be innocent. Three begin to demand explanation. Six or seven, spread across multiple evidence domains, constitute a diagnostic profile that research has shown to be highly predictive of deception.

What the Research Shows

The empirical case for SUE is substantial. Maria Hartwig’s doctoral dissertation at the University of Gothenburg, published in 2005, provided the foundational experimental evidence. In one study, participants who had committed a mock crime were interviewed either by SUE-trained or untrained interviewers. The untrained interviewers, who disclosed evidence early and relied on behavioral observation, achieved accuracy rates in the typical 50 to 60 percent range. The SUE-trained interviewers, who withheld evidence and measured SEIs, achieved accuracy rates above 85 percent.

Subsequent studies have replicated this finding with variations in crime type, evidence strength, suspect preparation, and interviewer experience. Aldert Vrij, a professor of applied social psychology at the University of Portsmouth and one of the most cited deception researchers in the world, has published extensive meta-analytic work confirming that information management strategies like SUE produce reliably superior deception detection compared to behavioral observation alone.

A 2014 meta-analysis by Hartwig, Granhag, and Luke examined the full body of SUE research and found a consistent, statistically significant advantage for the technique across studies. The effect was not marginal. SUE-trained interviewers outperformed comparison conditions by a wide enough margin to suggest that the information asymmetry paradigm represents a genuine advance in investigative practice, not an incremental improvement.

Research by Clemens, Granhag, and Strömwall extended the framework to show that SUE’s effectiveness holds even when suspects are given advance warning that evidence may exist. The technique’s power does not depend on the suspect being naive. It depends on the suspect not knowing which specific evidence the investigator possesses, a condition that holds in nearly every real investigation.

SUE versus Reid: Two Philosophies of the Interview Room

The dominant interrogation framework in American law enforcement for the past six decades has been the Reid Technique, developed by John E. Reid and Associates in the 1960s. The contrast between Reid and SUE is not a matter of degree. It is a difference in kind.

The Reid Technique operates on a confrontational model. The investigator begins from a presumption of guilt, typically based on a Behavioral Analysis Interview that purports to identify deceptive subjects through verbal and nonverbal cues. Once the investigator has decided the suspect is lying, the interrogation phase begins. The interrogator presents a theory of the crime, blocks the suspect’s denials, offers psychological “themes” that minimize the moral severity of the act, and creates an environment where confession becomes the path of least resistance.

Reid works through pressure. It assumes the investigator can accurately determine guilt before the interrogation begins, an assumption the deception detection literature does not support. And it produces a well-documented category of harm: false confessions.

The Innocence Project has documented hundreds of wrongful convictions in the United States. In roughly 29 percent of DNA exoneration cases, the defendant had provided a false confession or a false incriminating statement. Many of these confessions were extracted using Reid-style interrogation techniques, where sustained psychological pressure, combined with minimization and maximization tactics, overwhelmed the suspect’s resistance regardless of their actual guilt or innocence.

SUE operates on a fundamentally different set of assumptions. The investigator does not begin from a presumption of guilt. The investigator begins from a presumption of information asymmetry. The goal is not to break the suspect down but to measure the relationship between the suspect’s account and the available evidence. The interview is diagnostic rather than persuasive. The technique does not pressure the suspect into a confession. It allows the evidence to reveal whether the suspect’s account is truthful or deceptive.

Because SUE does not rely on psychological coercion, it does not produce the conditions that generate false confessions. A truthful suspect interviewed with the SUE technique will produce a narrative that aligns with the evidence, and the technique will correctly identify them as truthful. The system protects the innocent precisely because it measures facts rather than manipulating emotions.

The Chris Watts Interview: SUE in Practice

The Chris Watts interrogation illustrates how the core logic of SUE operates in a real investigation, even when investigators are not formally applying the protocol by name.

When CBI and FBI agents sat down with Watts on August 14 and 15, 2018, they held a devastating piece of evidence: the Vivint doorbell footage from the neighbor’s security camera. That footage showed Watts backing his truck into the garage at 5:27 AM and making multiple trips to load objects into the truck bed. No one else left the house.

Watts had already told Officer Coonts, on camera, that Shanann left with the girls around 5:15 AM. He had repeated this story to reporters. He was committed to a timeline that the footage made impossible.

The investigators did not lead with the footage. They asked Watts to describe his morning again. They asked him about the garage. They asked him about his routine with the truck. They asked open-ended questions designed to give Watts every opportunity to either adjust his story or commit more deeply to the version the evidence would later contradict.

When the footage was finally disclosed, Watts had no room. His free narrative and his specific answers had produced multiple Statement-Evidence Inconsistencies. The gap between his account and the documented reality was not a matter of imprecise memory or minor discrepancy. His entire timeline was a fabrication, and the footage proved it.

The Watts case also demonstrates the limits of the investigators’ approach. While the evidence management strategy was textbook SUE, the later stages of the interrogation incorporated Reid-style techniques, including the “maternal approach” by Agent Lee, which offered Watts a psychologically palatable false narrative to confess to. This resulted in his initial, fabricated confession in which he blamed Shanann for killing the girls. The full truth did not emerge until a prison interview months later.

A pure SUE approach, one that continued measuring inconsistencies rather than offering narrative outs, might have produced a different immediate result. But the case demonstrates the power of the technique’s core principle: when the investigator controls the timing of evidence disclosure, the suspect’s own words become the most damning testimony.

Application Beyond the Interview Room

The SUE framework has implications that extend beyond criminal investigation. Any context where one party may be withholding or misrepresenting information, and the other party holds evidence relevant to the truth, is a context where SUE’s principles apply.

Investigative journalism operates in precisely this space. A reporter working a story about institutional misconduct, financial irregularity, or official deception will often interview subjects who have reason to minimize, omit, or fabricate. The reporter, like the investigator, may hold documents, records, or source testimony that the subject does not know about.

The best investigative reporters have always practiced a version of SUE intuitively. You ask the question before you reveal what you know. You let the official deny the meeting before you produce the email showing they attended. You ask the executive to describe the decision-making process before you introduce the internal memo that contradicts every word they just said.

The SUE framework gives this intuition a structured methodology. Map your evidence before the interview. Plan your questions in layers, from open to specific. Withhold your strongest material until the subject has committed to a narrative on the record. Then disclose, and let the inconsistencies speak for themselves.

The Cognitive Interview, designed for cooperative witnesses, pairs naturally with SUE in this context. Use cognitive retrieval techniques to maximize the quality and quantity of information from willing sources. Use SUE’s evidence management strategy when the source may be adversarial or self-serving. The two methods address different interview challenges, and the most effective practitioners deploy both.

Why SUE Matters for Wrongful Conviction Prevention

The wrongful conviction crisis in the United States is, in significant part, an interrogation crisis. When investigators use methods that pressure suspects into confessions regardless of guilt, innocent people go to prison. The Reid Technique’s track record on this point is not a matter of debate. It is a matter of documented cases, DNA exonerations, and ruined lives.

SUE offers an alternative that is not merely less harmful but affirmatively protective. Because the technique measures the relationship between a suspect’s statements and objective evidence, it provides a structural safeguard against false convictions. An innocent person’s account will tend to align with the evidence. The more evidence an investigator holds, the more clearly SUE distinguishes between truth and deception, and the more reliably it protects the innocent suspect from a process that might otherwise destroy them.

This matters at every stage of the justice system. It matters in the initial interview, where the decision to charge or release begins to form. It matters in pretrial proceedings, where the strength of the evidence against the suspect is evaluated. It matters in the courtroom, where the content of the suspect’s interview will be scrutinized by judge and jury. At each point, an interview conducted under the SUE framework produces a record that is more transparent, more evidence-grounded, and more resistant to the cognitive biases that drive wrongful outcomes.

Several countries have begun incorporating SUE principles into their national interview training standards. The United Kingdom’s PEACE model, which replaced Reid-style interrogation in the early 1990s, shares SUE’s emphasis on information gathering over confession extraction. Scandinavian countries, where the technique originated, have integrated it into police training curricula. In the United States, adoption has been slower, but research institutions and reform-oriented law enforcement agencies have begun recognizing the technique’s value.

The SUE technique does not promise certainty. No method does. Human deception is complex, and even the best information management strategy can be defeated by a suspect who is well-prepared, psychologically disciplined, or simply lucky in their guesses about what evidence exists. But the technique shifts the odds dramatically. It replaces intuition with measurement, pressure with strategy, and accusation with diagnosis. In a system where the consequences of error are measured in decades of human life, that shift matters.

Sources

• Granhag, P.A., & Hartwig, M. (2008). A new theoretical perspective on deception detection. Psychology, Crime & Law, 14(3), 189-200.
• Hartwig, M. (2005). Interrogating to detect deception and truth: Effects of strategic use of evidence. Doctoral dissertation, University of Gothenburg.
• Hartwig, M., Granhag, P.A., Strömwall, L.A., & Kronkvist, O. (2006). Strategic use of evidence during police interviews. Law and Human Behavior, 30(5), 603-619.
• Hartwig, M., Granhag, P.A., & Luke, T. (2014). Strategic use of evidence during investigative interviews. In Credibility Assessment (pp. 1-36). Academic Press.
• Vrij, A. (2008). Detecting Lies and Deceit: Pitfalls and Opportunities (2nd ed.). Wiley.
• Vrij, A., & Granhag, P.A. (2012). Eliciting cues to deception and truth. Journal of Applied Research in Memory and Cognition, 1(2), 110-117.
• Clemens, F., Granhag, P.A., & Strömwall, L.A. (2011). Eliciting cues to false intent. Law and Human Behavior, 35(6), 512-522.
• Meissner, C.A., et al. (2014). Accusatorial and information-gathering interrogation methods. Journal of Experimental Criminology, 10(4), 459-486.
• Leo, R.A. (2008). Police Interrogation and American Justice. Harvard University Press.
• Innocence Project — DNA Exonerations in the United States.