Pär Anders Granhag and Maria Hartwig at the University of Gothenburg started from an observation about strategy rather than about behavior. Guilty and innocent suspects enter an interview with different problems, and therefore adopt different strategies, and the strategies can be exposed.
The guilty suspect's problem is that certain facts are incriminating and they do not know which of them the interviewer has. Their strategy, consistently observed, is avoidance and denial: do not mention the incriminating facts, and if pressed, deny them.
The innocent suspect's problem is different. They have nothing to conceal, and their strategy — Hartwig and Granhag call it the illusion of transparency and the belief in a just world — is to tell it like it happened. Innocent suspects report incriminating-seeming facts freely, because they know the facts are innocuous and assume everyone else will see that too.
Strategic Use of Evidence exploits the gap. The interviewer holds back what they know. The suspect gives a full account, unprompted and unwarned. Only afterwards is the evidence disclosed, and the account is compared with it.
A guilty suspect, guessing at what is known, will have omitted or denied things that turn out to be documented. An innocent one will have mentioned them. The measurable output is statement-evidence inconsistency, and unlike the behavioral cues in Part 2 it is not a small effect: in Hartwig's training studies, interviewers trained in SUE reached accuracy rates in the region of eighty-five percent, against roughly chance for untrained interviewers who disclosed evidence early.
That is the largest well-supported improvement in deception detection in this guide, and its mechanism is worth being clear about, because it is not a way of reading people. It is a procedure that produces an artifact — a discrepancy between a statement and a document — that can be examined by anyone.
The Shift-of-Strategy extension goes further, disclosing evidence in a planned sequence and observing how the suspect's account changes in response, on the reasoning that a guilty suspect must continually revise while an innocent one has nothing to revise.
Two operational conditions are essential and both are frequently violated in practice.
The evidence must be withheld until after the free account. An interviewer who opens with we know you were there has destroyed the instrument, because the suspect can now build an account consistent with what has been revealed. This is the single most common error, and it is what most people do instinctively — leading with what you know feels like strength.
And the account must be full and specific before disclosure, which means asking for detail on exactly the points the evidence covers, without signaling why.
The technique's discipline is patience: knowing something and not saying it, for as long as it takes.
Cross-ref: Scharff technique chapter