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The extraordinary capabilities of the canine nose are increasingly being used by law enforcement agencies in many countries to solve and reconstruct crimes. As a result, this type of forensic evidence can be and is still being challenged in the courts. So far, only a few publications have addressed the jurisprudence concerning mantrailing. We provide an overview of the jurisprudence in Germany and the USA, as well as insights from France. Relevant databases were searched, and 201 verdicts from Germany and 801 verdicts from the USA were analyzed. As a result, 16 published verdicts on the topic of mantrailing were found for Germany, and 44 verdicts since 2010 were found for the USA. The use of mantrailers and human scent discrimination dogs is employed in the investigative process in all three countries. The results derived from these methods are admissible as evidence in court, albeit not as sole evidence.

•Individual scent article allows mantrailers to differentiate an odour trail.•Saliva as well as DNA extracted from whole blood are sufficient as a key stimulus.•Mantrailing appears as a reliable and useful tool for law enforcement authorities. Specially trained dogs have long been used by law enforcement agencies to help in criminal investigations and in searching for missing persons. Still, it is unclear which components of human scent released into the environment contribute to successful searches of individuals. In this study, saliva and axillary sweat samples were taken from a total of 190 people. Additionally, DNA was extracted from whole blood of seven different people and used as an odour sample as well. Overall 675 tests (trails) were performed during a period of 18 months. The ability to track individuals with the odour samples mentioned above was examined with seven dogs, four of which were specially-trained dogs (mantrailer) from the Saxony Police. Results indicated that specially-trained police dogs can track a person with an average success rate of 82% and correctly identify the absence of an odour track with an average success rate of 97% under various conditions. Private rescue dogs were less successful with an average success rate of 65% and 75% respectively. These data suggest that the potential error rate of a well-trained handler team is low and can be a useful tool for law enforcement personnel. Saliva, as a reference odour source, was found to be particularly suitable for the search. The results of the study suggest that the components contained in axillary sweat, saliva and DNA extracted from whole blood are sufficient, serving as a key stimulus for individualized searches.

Here transfer performance is contrasted with baseline training performance to determine whether a relational solution strategy is learned from the systematic pseudo matching-to-sample procedures commonly used to train human-scent-matching dogs. Evidence indicates that due to the lack of constraints to control against simple discrimination solutions, dogs trained with systematic pseudo matching-to-sample arrangements do not learn to use the scent sample as a signaling cue and do not learn about the matching relationship between the scent sample and matching comparison. Moreover, during pseudo matching-to-sample training, dogs may learn to ignore both the scent sample and the discriminative dimension of human scent, such as genetic information. Thus, during subsequent random control matching-to-sample (MTS) conditional discrimination training, learning about the matching relationship between the individual-unique information on the scent sample and matching comparison can be retarded. Failure to identify the solution strategy that human-scent-matching dogs must learn in order to perform accurately and reliably during operations and to distinguish between simple discrimination, random control MTS conditional discrimination, and systematic pseudo matching-to-sample has been a major drawback to the advancement of scent-matching dogs and is a contributing factor to the continued controversy surrounding their use and reliability.