Scent lineups compared across eleven countries: Looking for the future of a controversial forensic technique

Abstract

A scent lineup is generally a procedure whereby a dog's alerting behavior is used to establish that the dog detects two scents, one from a crime scene and one from a suspect, as deriving from the same person. The aim of this article is to compare methodologies of using dogs in scent lineups as a means of identifying perpetrators of crimes. It is hoped that this comparative approach, looking at countries where the method is currently or has in the past been used, will help determine what issues should be addressed in order to assure that the scent lineup will have a future as a forensic technique. Participants from eleven countries—Belgium, The Czech Republic, Finland, France, Germany, Hungary, Lithuania, The Netherlands, Poland, Russia, and the U.S.—completed a survey questionnaire regarding key aspects of the scent lineup procedures used by the police in their countries. Although there was broad overlap on certain matters, such as the use of control and zero trials, collection of decoy scents from individuals of similar gender and race as the suspect, materials for holding scent, frequency of cleaning and changing stations, and use and timing of rewards, there were significant differences in the degree of blindness required, who calls an alert (handler or experimenter), and whether handlers can work with more than one dog. The gap between recommendations and results available from the scientific literature and procedures used in police practice was greater for some countries than others, even taking into account that some scientific methodologies might be expensive or impractical given agency resources. The authors make recommendations about how to go forward if scent lineups are to remain a valid forensic technique.