"Preface Prioritizing suspects or persons of interest (POIs) is nothing new. As long as investigators have been investigating cases involving multiple suspects, they have been deciding whom on their list they feel is the most likely to have committed their offence(s). Sometimes this is based on the investigation and forensic evidence, and often times on just a gut feeling or intuition. This approach has served investigators well over the years when the suspect/ POI pool was relatively limited. However, when that pool becomes very large as is typically the case in high profile investigations, establishing a priority ranking is more difficult but this is when it is most important. It allows management to direct investigative resources to those suspects/POIs who are most likely to have committed the offence(s). This is an effective and efficient use of resources. It not only may save a significant amount of money, but more importantly it could save additional victims. The problem with using the 'gut feeling' or 'intuitive' approach to prioritizing suspects was illustrated by a research experiment carried out by the author. Twenty-nine files containing background information on 29 individuals who had been identified as POIs in a major serial homicide investigation were given to three very experienced investigators assigned to that investigation. They were asked to evaluate each of the files based on their experience and intuition as to what they felt the priority rating should be on each of the files (POI-1, POI-2 or POI-3). They did this exercise independently of each other without discussion. The results were as follows They all agreed on 13 files. Twelve of those files were in the low priority range (POI-3)"-- Provided by publisher.