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Verification of a New Canine Training Method for the Human Scent Identification
Haffner, Martin ; Pinc, Ludvík (advisor) ; Jaroslav, Jaroslav (referee)
Scent identification is a forensic method which is used in many countries. Principle of this method is always the same, but in each country are used different processes. This method is based on comparison of an odor collected at the crime scene and an odor collected from the suspect.
The aim of this study was to verify new methodology designed by Dr. Adee Schoon. This method consists of different dog training methodologies. In the commonly used method the dog gets an odor from his handler to sniff at before each particular line-up. This is match to sample method. That means the dog is able to compare two samples from the same person. In the modified methodology a dog once sniffs at the single odor placed on the ground. After distracting odors are added the dog is supposed to alert to the matching odor again. Thus the method under testing is more like based on the detection of target odor than on match-to-sample scenario.
Human odor samples were collected from palms of hands, metal tubes and the object belonging to the same person. Experimental persons were asked to wash their hands and let them to dry freely. At first, sorbent material Aratex was placed to palms of these persons for fifteen minutes and then it was closed and sealed in odorless glass jars. Then the metal tubes were given to hold to experimental persons for five minutes. After this time metal tubes were placed into glass jars with odorless Aratex which was later used as scent samples. The metal tubes were removed from glass jars after thirty minutes. Scent samples from objects were collected similarly as from metal tubes, these samples served as a corpus delict. The starting scent samples and target scent samples were collected by a different persons. Additional odors were collected using the same protocol and under similar conditions, so none of the odor samples in a line-up were more attractive for the dog than the others.
For the training three years old female belgian shepherd malinois was used, trained by the author of the project. Intrinsic matching procedure was always three times repeated. At first, the dog sniffed at the scent sample from the palms of hands. The line-up was arranged of scent samples collected from metal tubes and objects. One of these scent samples was the target scent (metal tubes). After comparison of metal tubes scents, the target scent was replaced by a scent sample collected from corpus delicti. In case the dog correctly indicated target scent, the result was recorded as correct.
For statistical evaluation Bernoulli distribution was used (P < 0.01). Over the whole experiment only one dog was used, and so it cannot be concluded that this method is easier for the dog than the traditional one, however the study demonstrated that such a method is basically usable as a tool by which dogs can be trained to identify individual human scents. Fischer´s test did not show any differences between comparisons based on the type of an object.
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