Human scent identification by police dogs

Odorology is a forensic technique that uses specially trained dogs to compare and identify human odors. The aim is to identify the perpetrators or victims of criminal offences who may have left their scent on a crime scene or object, in the same way as their DNA or papillary print. In this way, the odor taken from the object or crime scene is compared with the odor of a suspect.

The "odorology" group was created in 2000 within the Direction Centrale de la Police Judiciaire (Sous-Direction de la Police Technique et Scientifique, SDPTS at Écully); it is the only laboratory in France to have applied the odorology technique, imported from Hungary, since 2003.

As practiced at SDPTS, this technique is based on indirect identification between two odors taken from supports. This avoids any subjectivity on the part of the dogs towards an object or an individual, and enables odors to be preserved for long periods.

The rigorous application of training procedures to the dogs of the SDPTS dog squad for the identification of human odours shows that, after a period of two years, the animals no longer make errors in recognizing two odours belonging to two different individuals. Furthermore, analysis of the results obtained on all the dogs since 2003 suggests that the olfactory sensitivity of the dogs improves with training, reaching a level that enables them to recognize two different odors from the same individual in an average of 85% of cases.

The data from this study show that rigorous monitoring of all procedures by the brigade's dogs leads to reliable and reproducible identification performance, which should be considered by magistrates as evidence in legal proceedings, in the same way as papillary or DNA identifications.

The aim of this article is to describe in detail the principles underlying the learning of human odor identification. Starting with the anatomical and physiological characteristics of the canine olfactory system, the article traces the use of dogs in tracking human odors throughout history. The body of the article then describes in detail the various phases of training developed by the SDPTS dog squad to train police dogs to identify human body odours. Finally, while the discussion of the results obtained since 2003 with the odorology technique shows that, combined with their great memorization capacity, the exceptional olfactory acuity of dogs can be used to prove the presence of an individual at a crime scene, it can also serve other causes in the public safety field, as well as in the medical field.