Evidence-based is a term that is tossed around frequently in investigative circles, but what does it really mean? How do investigaters filter the vast amount of research and decide what to integrate into their work? This blog will provide two common scenarios of “evidence” being incorrectly applied and a strategy to ensure your work is truly evidence-based.

The first scenario involves the use of pseudo-science. In our world of readily accessible data, it is well known that one can find a study to support almost any claim. Proponents of NeuroLinguistic Programing (NLP) assert that certain eye movements are indicative of truth-telling or lying. This notion is popular, likely due to the appeal of simplicity. NLP holds that moving your eyes up and to the left is a sign of truth-telling, while moving your eyes up to the right is a sign of lying. They use very basic and simplistic knowledge about brain functioning to support this claim, which makes their arguments sound like it is based in science. However, researchers have conclusively debunked this theoryi, labelling it as pop-psychology. Nevertheless, this idea continues to be promoted as a reliable way to detect deception. This is an example of a practice being adopted despite the lack of supporting research – in other words, despite the lack of sound evidence.

The second scenario involves the misapplication of scientifically-based knowledge. Recently, structured decision-making tools (SDM tools) have been introduced to front line investigators as many agencies strive to conduct more accurate and reliable risk assessments (e.g., SDM tools for domestic violence). These assessment tools were validated under certain conditions and they were designed to be used after the facts of a case have been gathered. In other words, only after reliable information has been collected can these tools be used in a valid manner. However, in some jurisdictions, investigators use these SDM tools in the information gathering stage. As SDM tools have set criteria, investigators (likely in an attempt to be efficient) incorrectly use them as an interview guide; or worse, as a scripted set of questions so they can complete a form. This is an example of a practice being adopted without understanding the original purpose of the SDM tool – which was to help investigators make better decisions, not to develop leading questions.

One strategy to ensure that your practice as an investigator is evidence-based is to read well conducted, peer reviewed research reports from reputable publishers that pertain to your
investigative area. In doing so, the question, “Why am I doing this? Why should I follow this procedure?” will likely be answered. Although this may appear to be an onerous task, in the decision-making context, it is the best investment an investigator can make. This strategy comes down to the basic concept that you need to understand the mechanics behind what you are doing, before you can do it well.

i Wiseman R, Watt C, ten Brinke L, Porter S, Couper S-L, Rankin C (2012) The Eyes Don’t Have It: Lie Detection and Neuro-Linguistic Programming. PLoS ONE 7(7): e40259.
https://doi.org/10.1371/journal.pone.0040259