K9 Suspect Discrimination: Training and Practicing Scent Identification Line-Ups

Using K9s for scent discrimination has been part of the forensic repertoire used to solve crimes for a number of decades in several European countries. Over the years, police forces have refined their approach to scent discrimination to reduce errors and make it as legally accountable as possible. Authors Adee Schoon and Ruud Haak emphasize that the dog does not pinpoint a suspect as the perpetrator, but merely indicates that there is or is not a scent connection between crime-scene evidence and the suspect. They provide detailed training methods and working methodologies for handlers who want to train their dogs in this important work, as well as procedures for gathering scent evidence from the scene of the crime. A detailed history also shows how methods have developed over the years, and why some procedures were no longer acceptable and needed to be changed.

Introduction

Linking the odor a perpetrator left at a crime scene to the odor of a person suspected of that crime is the most challenging training one can give a dog. Few dogs have the mental stability and the cognitive ability to be able to learn this. Few handlers are able to train a dog to a consistent high level, and stand up against the pressures of judicial procedures and evidence gathering. Perhaps this is why police forces and courts in many countries are so reluctant to use this exceptional ability of dogs. And perhaps this book will change that.

The book first examines the roots of scent identification line-ups, as they are now called. It then describes some necessary background information: what is a person’s individual odor, how do dogs learn, and what scientific work has been done with dogs in discriminating human odor. It addresses all sorts of questions that can be asked in court, building on scientific work conducted predominantly in the Netherlands and Poland. It provides a training guideline, and describes the differences and similarities of scent identification line-ups in different European countries. The reliability of line-ups is put into perspective by comparing it with other kinds of forensic evidence. And finally, it provides a checklist for implementing scent identification lineups as a forensic tool.

With such a range of subjects, the book is of interest for a wide group of people. The book is of importance to all dog handlers with a real interest in dogs, since it can enlarge their thinking on training and what can be achieved with dogs. It will also give them insight into the use of dogs for evidential purposes and the criteria that must be met there. It is also of interest to police forces and forensic institutions, since it describes a method of investigation that, implemented correctly, will provide information impossible to collect in any other way. It is of interest to lawyers, public prosecutors and judges, since it shows which points are relevant, how to establish reliability, and hopefully answers some of the questions they may have.

This book sums up the experience of many people in many organizations. The list of individuals to thank is endless, so we will thank their organizations. First of all we sincerely thank the Canine Unit of the Netherlands National Police Agency. The history of line-ups was collected there, the training guide was developed with their group of scent identification handlers, and the implementation checklist was the result of brainstorming sessions with the head of the Unit. The Ministry of Justice and the Netherlands National Police Agency financed the scientific work done in the Netherlands, and the Leiden University had, and has, an important role here. Handlers of police scent identification dogs in the Netherlands, Germany and Denmark have made this scientific research possible by participating in experiments. The forensic laboratory of Poland, and the scent identification departments of Hungary, Germany, Denmark and Belgium have all at some time contributed to this book through discussions, experiments, protocols and/or pictures. The Netherlands National Police Agency, the Netherlands Police Museum and the Netherlands Image and Sound Archives have contributed pictures for which we thank them. And we thank the people we have asked to read (parts of) the book, and who have contributed their suggestions and corrections.

We are very pleased that we have been able to write this book as a sequel to a number of others on working with dogs. We hope that many people will enjoy reading it as much as we enjoyed writing it. Our families, who have had to live with us during this time, can now have us back.