Vulnerable populations don't need weaker techniques; they need better ones. What a day teaching guardianship investigators revealed about the research — and why it applies far beyond law enforcement.
I recently finished teaching a day-long course with the National Guardianship Association in their National Investigator Training Program, and the same question kept surfacing throughout the day: "Do these science-based interviewing techniques really work with vulnerable individuals — people with intellectual disabilities, mental health conditions, dementia, developmental disorders?"
My answer was I'm not sure. My opinion was quality communication will work anywhere, but I told them I would research that more and provide them an answer and research to support it. I came home and got busy and the answer is unequivocal: Not only do they work — they're absolutely essential.
But here's what struck me most about these questions: They revealed a fundamental gap in how we think about investigative interviewing. Many practitioners still operate under the assumption that vulnerable populations require a different approach — something softer, more simplified, perhaps less rigorous. The research tells us something entirely different: Vulnerable populations don't need weaker techniques; they need better techniques. And science-based interviewing represents exactly that.
Let's be honest about where we are. Despite decades of research demonstrating the effectiveness of open-ended questions, they make up less than 1% of questions in actual police interviews — and are completely absent in over 60% of interviews studied. We know that open-ended questions elicit responses six times longer than probing questions and nine times longer than yes-no questions. Yet we continue to rely on closed, leading, and confirmatory questions that box people into our preconceived narratives.
Now add vulnerability to this equation. When you interview someone with an intellectual disability using traditional interrogation approaches — rapid-fire questions, yes-no formats, leading questions, constant interruptions — you're not just getting poor information. You're actively exploiting cognitive vulnerabilities that make these individuals highly susceptible to suggestion, acquiescence, and providing false information to please authority figures.
The research is stark: Individuals with intellectual disabilities show dramatically increased error rates when asked leading or closed questions. They're prone to acquiescence — saying "yes" regardless of question content. They struggle with abstract concepts, complex sentence structures, and the rapid pace of traditional interviews. They may confabulate to fill memory gaps when pressured for answers they don't have.
And here's the kicker: None of this is about the witness. It's about the technique.
Science-based interviewing wasn't designed specifically for vulnerable populations, but it might as well have been. The ethical foundations and methodological rigor that make these techniques effective for everyone make them particularly protective for those with vulnerabilities.
Consider the core principles:
Research with children and adults with intellectual disabilities demonstrates that open-ended questions elicit more accurate and abundant information than closed or specific questions. When you ask "Tell me what happened" instead of "Did he touch you?", you reduce suggestibility, minimize acquiescence, and allow the person to describe events in their own words without contamination.
The RAND Corporation found that law enforcement officers interrupt witnesses approximately every seven seconds. Seven seconds. That's barely enough time for anyone to formulate a thoughtful response, let alone someone with cognitive processing differences. Science-based interviewing demands we combat this interruption problem by deliberately allowing 7-10 seconds of silence after responses — and even longer for individuals with processing needs. Slower is faster when it comes to gathering reliable information.
When you simplify vocabulary, use short sentences, avoid abstract concepts, and ask about specific observable events rather than generalizations, you're not dumbing down the interview — you're removing barriers to accurate communication. This benefits everyone, but it's absolutely critical for individuals with communication vulnerabilities.
Vulnerable individuals are often accustomed to authority figures not believing them, talking over them, or making decisions for them. When you build genuine rapport, provide clear explanations, validate their experiences, and demonstrate patience, you create an environment where truthful disclosure becomes possible.
The evidence supporting science-based techniques with vulnerable populations is compelling:
Studies by Milne and Bull demonstrated that cognitive interview techniques increase accurate recall in individuals with severe intellectual disabilities without increasing incorrect details. Research by Henry and Gudjonsson showed that narrative practice — having individuals practice answering open-ended questions early in the interview — significantly increases accuracy for those with intellectual disabilities.
Kebbell and Hatton's work revealed that when appropriate techniques are employed, individuals with intellectual disabilities can provide accurate and reliable testimony. The problem isn't the witness's capacity — it's the interviewing method.
Research on children (which applies to adults with similar developmental levels) consistently demonstrates that open-ended invitations produce more information and higher accuracy than specific or closed questions. The NICHD Protocol, built on these principles, has proven remarkably effective across vulnerable populations.
Even more striking: Studies show that many wrongful convictions involving vulnerable individuals can be traced directly to inappropriate interviewing techniques — leading questions, suggestive prompts, failure to accommodate communication needs, and exploiting acquiescence through yes-no questions.
During my National Guardianship Association session, I realized something important: This isn't just a law enforcement issue. Guardianship professionals interview vulnerable adults to assess capacity, understand wishes, and investigate concerns. Corporate investigators interview employees with disabilities about workplace incidents. HR professionals conduct sensitive interviews with staff experiencing mental health crises. Healthcare providers gather information from patients with cognitive impairments. Compliance officers investigate allegations involving vulnerable parties.
All of these contexts involve information gathering. All of them involve individuals who may have vulnerabilities. And all of them benefit from — indeed, require — science-based approaches that maximize accurate information while protecting the integrity of both the process and the person.
The principles remain consistent across contexts:
Here's what keeps me up at night: Every day, investigators, auditors, compliance professionals, and others are conducting interviews with vulnerable individuals using techniques that research has proven unreliable, suggestive, and potentially harmful. Not because they're malicious — but because nobody trained them differently.
We know better. The research exists. The techniques work. Yet organizational leadership continues to tolerate — or worse, mandate — interviewing approaches that belong in the last century.
This isn't just about effectiveness, though effectiveness matters tremendously. This is about ethics. About justice. About treating vulnerable individuals with the dignity and respect they deserve while pursuing truth rather than confirmation of our biases.
When we use leading questions with someone who has an intellectual disability, we're exploiting a cognitive vulnerability. When we interrupt someone with processing delays every seven seconds, we're preventing meaningful communication. When we fail to provide appropriate accommodations, we're discriminating under the guise of "normal procedure."
Science-based interviewing techniques don't lower standards for information quality — they raise the quality of our practice to meet the needs of all individuals, regardless of vulnerability.
It's time for leadership across all sectors — law enforcement, corporate security, human resources, compliance, guardianship, healthcare — to stop paying lip service to best practices and start implementing them.
The questions I received at the National Guardianship Association weren't just about technique — they reflected genuine concern for doing right by vulnerable individuals. That concern is admirable. Now it needs to translate into action.
We have the research. We have the techniques. We know what works. The only thing missing is the organizational will to implement what we know to be true: Science-based interviewing isn't just appropriate for vulnerable populations — it's the only ethical, effective approach that serves justice.
The individuals we interview — whether they have intellectual disabilities, mental health conditions, cognitive decline, or other vulnerabilities — deserve nothing less than our commitment to techniques that respect their dignity while pursuing truth. They deserve interviewers who are trained, patient, and genuinely curious rather than confirmatory.
And they deserve leadership that values getting it right over getting it done.
Training is a first step! It is what 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. 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.
Are you conducting interviews with vulnerable populations? What challenges have you encountered? What training resources would be most valuable? Share your thoughts in the comments.