People tell the truth more readily when they believe you already know it. Here's the research behind the Scharff technique — and how demonstrating genuine competence, not bluffing, changes what interviewees are willing to reveal.
In my previous three articles, I demonstrated that behavioral lie detection doesn't work (achieving only 52% accuracy), then explored Dr. Christian Meissner's framework for assessing the interviewee's credibility through access and knowledgeability — questioning whether witnesses could actually observe and understand what they claim.
Today, I'll explore the complementary dimension: how your competence and preparation as the interviewer facilitates truthful disclosure. This is the other side of the credibility equation, and it's equally grounded in psychological research.
The fundamental insight: people are more likely to provide truthful information when they perceive the interviewer as knowledgeable, competent, and already well-informed about the situation. This isn't manipulation — it's a psychological reality that science-based interviewers can leverage ethically through thorough preparation and strategic communication.
Research on the Scharff technique — derived from analyzing the methods of WWII Luftwaffe interrogator Hanns Scharff — reveals a powerful principle: at the very core of the technique is the "illusion of knowing it all" tactic, which aims to inflate a source's perception of how much knowledge an interviewer holds about the event to be discussed.
When sources believe the interviewer already possesses substantial knowledge, something psychologically significant happens: sources underestimate how much new information they're revealing and find it more difficult to determine what the interviewer wants to learn. They reason: "The interviewer already knows this, so I'm not really giving anything away by confirming it."
This isn't about deception or bluffing. Scharff avoided coercive methods and became known for his equality-oriented approach. He didn't press for information but would tell stories, related in such a fashion as to encourage conversation and leave openings for the source to fill in.
The research is unequivocal: meta-analytic review supports the conclusions that Scharff's technique is effective at eliciting more new information, leading people to perceive the interviewer as more knowledgeable, and inducing people to underestimate how much information they have revealed.
To understand why interviewer competence matters, we must first understand how sources behave during interviews. Scharff identified at least three general behaviors sources use to avoid providing information: (1) I will not tell very much, (2) I'll try to figure out what they are after and not provide that information, and (3) it is meaningless to deny or hold back what they already know.
Notice the third strategy: sources calculate whether withholding information serves any purpose. When they perceive the interviewer already knows substantial information, continued withholding appears futile and potentially counterproductive.
Research shows that sources approached with explicit questions believe the interviewer knows very little about the topic. In such cases, sources perceive that almost everything they reveal will advance the interviewer's knowledge. In direct contrast, the Scharff technique influences sources to perceive the interviewer as knowledgeable.
This explains a phenomenon every investigator has experienced: when you demonstrate command of facts early in an interview, resistance decreases and cooperation increases. This isn't coincidence — it's psychology.
Here's the critical point: you cannot project competence you don't possess. The "illusion of knowing it all" only works if you actually know substantial information. This connects directly to my previous articles on planning.
I've emphasized that fewer than one in ten interviews receives adequate planning. Research shows this matters profoundly: military intelligence officers trained in the Scharff method and who presented 50% or more of previously known information upfront were perceived by sources as significantly more knowledgeable than untrained officers, most of whom presented less than 30% or no information at all.
The math is straightforward: if you haven't invested time researching the case thoroughly, you have nothing substantial to present. Without substantial knowledge to demonstrate, you cannot create the perception of competence that facilitates disclosure.
This is why my "pound of planning" principle isn't just about organization — it's about enabling the psychological conditions that make truth-telling feel safe and inevitable to interviewees.
Demonstrating competence requires strategic planning and thoughtful execution. Research identifies several specific tactics:
Research compared two approaches: explicitly stating "I already know most of the important information" versus just starting to present what you know. The "just start" approach was more effective — sources believed the interviewer had more knowledge and searched less actively for gaps in that knowledge.
Practical Application: Instead of opening with questions, open by demonstrating what you know:
Notice what this accomplishes:
This isn't bluffing — you're stating facts you've verified through planning and investigation.
Rather than asking direct questions, the interviewer presents claims within a narrative that the source might confirm or disconfirm. The advantage is that sources might be more willing to respond to a claim than to an explicit question, as confirming a claim might be viewed as "I only confirmed what they already knew," and disconfirming a claim might be viewed as "I only told them what they had wrong."
"Where did you go after leaving the warehouse?" — broadcasts that the interviewer doesn't know, inviting denial or a guarded answer.
"After leaving the warehouse, you drove to the industrial park on Route 23. We know the vehicle was there between 3:45 and 4:15pm." Confirm or correct — either way, information is gained.
The source now faces a choice: confirm (which feels like revealing nothing new) or correct (which feels like simply fixing an error). Either way, you gain information. If your claim is right, they've confirmed it. If wrong, their correction provides the accurate information.
This connects directly to my Time/Responsibility Continuum work: when interviewees ask "What evidence do you have?" responding with "The inquiry is complete, and the evidence clearly indicates your involvement" projects the same competence — you're demonstrating command of facts rather than fishing for information.
Scharff avoided coercive methods. Rather than demanding answers to questions, Scharff would tell stories, related in such a fashion as to encourage conversation and leave openings for the source to fill in.
This is critical: competence projection works synergistically with rapport. Scharff-trained officers were perceived as less eager to gather information but collected similar or more new information than untrained officers who asked many explicit questions, questioned reliability, pressured sources, and displayed disappointment.
The psychology is counterintuitive but powerful: appearing less eager to gather information (because you already know so much) actually produces more information than appearing desperate to learn (which signals you know little).
Practical Application: Your demeanor should communicate: "I already understand this situation comprehensively. I'm here to ensure I have the complete, accurate picture and to give you the opportunity to provide your perspective." Not: "I'm trying to figure out what happened and I need you to tell me." The former projects competence. The latter broadcasts ignorance.
The connection to SUE technique is profound. The hypothesized underpinnings of the Scharffian illusion of knowing it all are similar to and consistent with the theoretical conceptualization behind the Strategic Use of Evidence (SUE) technique, which aims to influence interviewees' behavior in part by controlling their perception of how much the interviewer knows.
Both techniques work by managing perceived interviewer knowledge — but in different ways:
Both require extensive planning. You must actually possess substantial knowledge to employ either technique effectively. And both work because they influence the interviewee's perception of what you know, changing their calculation about what to reveal.
The Time/Responsibility Continuum responses exemplify this principle. When asked "What's going to happen to me?" responding with "None of us can predict the future, but I know that when people tell the truth and lay all the information on the table, it's viewed much more favorably by decision-makers" accomplishes multiple goals:
This is interviewer competence in action.
Competence and rapport aren't separate — they reinforce each other. Research on rapport-based interviewing demonstrates that when interviewers project competence while maintaining respectful, professional demeanor, both trust and cooperation increase dramatically.
Think about your own experience: who do you trust more — someone who appears uncertain and poorly prepared, or someone who demonstrates mastery of relevant facts while treating you respectfully? The answer is obvious.
This is why superficial "rapport-building" techniques often fail. Asking about family or pretending to share interests without demonstrating professional competence feels manipulative. But genuine competence — thorough preparation, command of facts, sophisticated understanding — builds organic rapport.
People want to engage with skilled professionals. When you demonstrate you've done your homework, understand the situation comprehensively, and treat them with dignity, cooperation becomes the natural response.
Implementing interviewer competence strategies requires fundamental shifts:
You cannot fake competence. You must invest the time to actually know:
My previous planning articles detail this process. Without adequate planning, competence projection is impossible.
Move away from: "Tell me what happened."
Move toward: "Let me share what we've learned so far..." [present substantial knowledge] "...and I want to ensure I have your perspective to complete the picture."
This opening demonstrates competence immediately. The interviewee's calculation about cooperation changes in the first two minutes.
Reduce explicit questions like "Where were you?" or "What did you do?" Increase claims and narratives: "We know you were at the warehouse around 2:30pm. Walk me through what you were doing there." The first broadcasts ignorance. The second projects knowledge.
When interviewees resist or deny, traditional approaches often involve repeating questions more forcefully, displaying frustration or disbelief, or attempting to pressure through accusation.
Competence-based approaches involve calmly presenting additional known information, maintaining professional, non-pressing demeanor, and allowing silence for the interviewee to recalculate their strategy.
Research consistently shows the second approach produces more information with fewer ethical and legal risks.
As I've discussed in previous work, handling denials effectively requires projecting competence. When someone denies involvement:
"Really? Are you sure? Because I think you're lying." Projects uncertainty, invites argument.
"The inquiry is complete, and there's no doubt about what happened. I'm here to understand why it happened." Projects certainty, reduces debate.
The second response demonstrates the confidence that comes from thorough investigation and solid evidence.
Some might question whether creating an "illusion" of knowledge is manipulative. This concern deserves direct address:
First: You're not creating an illusion — you're accurately representing substantial knowledge gained through legitimate investigation. If you've properly prepared, you DO know a great deal.
Second: You're not promising outcomes, coercing confessions, or using deception about consequences. You're simply presenting what you know in a strategic manner that facilitates disclosure.
Third: Research shows this approach produces MORE reliable information and FEWER false confessions than accusatorial, confrontational methods. It's actually more ethical because it respects interviewee autonomy while creating conditions where truthfulness appears beneficial.
Fourth: The friendly, non-pressing approach fundamental to this technique treats interviewees with dignity. It's the opposite of coercive interrogation.
When applied properly, demonstrating competence is ethical persuasion grounded in genuine preparation. It's not manipulation — it's professionalism.
Let me illustrate how competence projection works in practice.
Scenario: Employee suspected of stealing company property.
Traditional Approach: "We're investigating some missing equipment. Do you know anything about it?" — projects ignorance, invites denial.
Competence-Based Approach:
What this accomplishes:
This is every principle — planning, competence projection, rapport-building, Time/Responsibility Continuum — integrated into a single opening.
Can you always achieve this level of preparation and competence projection? No. Some investigations provide limited information, time constraints prevent thorough planning, or evidence simply doesn't exist.
But the principle remains: the more knowledge you possess and effectively demonstrate, the more cooperation you'll receive. Even partial implementation produces better results than traditional question-based approaches.
And when you cannot demonstrate competence because you genuinely lack information, your investigation may not be ready for the interview. As I've emphasized about planning: if the interview matters enough to conduct, it matters enough to prepare properly.
Throughout this four-article series, we've progressed from destruction to construction:
These aren't separate techniques — they're integrated components of science-based interviewing. When you've properly planned, you understand what access and knowledgeability the situation requires. When you demonstrate your own competence, you facilitate the cooperation necessary to assess theirs.
The research is clear: people provide more truthful information when they perceive interviewers as knowledgeable, competent, and well-prepared. This isn't manipulation — it's psychology. And ethical application requires genuine preparation, not bluffing or deception.
After fifty years of research showing behavioral credibility assessment doesn't work, we need approaches that do. Demonstrating competence through thorough preparation and strategic presentation is one such approach — grounded in research, ethically sound, and practically effective.
The choice is yours: continue relying on intuition and behavioral cues that research shows don't work, or adopt evidence-based approaches that leverage psychology to facilitate truthful disclosure.
The science points clearly toward competence over intuition. It's time to follow where the evidence leads.
Like much of what I write about training is a first step! It is what has moved me beyond my blind spots (at least some of them). I can provide the training or recommend providers teaching science-based techniques. Do your research, find the right provider, maximize your training dollar investment. If you are a practitioner or a leader, don't get the same old legacy-based methods that have no empirical evidence supporting them. This is not the time to "do it as we have always done it." If you are in leadership, you have the same responsibility to know and apply these standards and find that training content that maximizes your team's effectiveness and accomplishes your mission.
Anderson Investigative Associates is positioned to custom-tailor science-based training to your specific needs. If you have any questions or would like to discuss the subject of this imperative transition, or any training need, please reach out. Additional issues pertaining to interviewing, auditing, and investigations can be found in other blogs and videos that we have produced and are contained in most blocks of instruction that our company presents.
If you have additional questions, comments, or have an interview topic you would like me to address, just let me know. In the meantime, be well, stay safe out there, and start investing in a transition which is ethical and effective. It will improve everything you do. It is time to improve your interviewing and communication skills, and not just in your work but throughout your life. If you need help getting ready, I know who could help.