The dissertation thesis consists of four papers that have been published in scientific journals. Study n. 1 The need to recover evidence from water is quite common in criminal investigation. The article deals with the possibility to collect human scent from such objects and with the ability of specially trained dogs to match such scent samples with scent samples collected from detained suspects. During an experiment, designed as a blind one, it has been proved, that human scent can survive on submerged objects and can be later used for scent identification. Study n. 2 To collect odors the Czech Republic Police use special fabric sorbents manufactured under the registered mark ARATEX. Before use the fabric sorbent is treated by water vapor sterilization. After the scent identification the sorbent is destroyed. The goal of the study was to verify if the vapor sterilization is effective enough to remove human scent that has already penetrated into the sorbent structure or in other words if the sorbent can be exposed to vapor sterilization and then used again. Specially trained dogs were used to match starting odors with target odors in the line-ups. The results showed that dogs are able to correctly match human odors even after they have being exposed to vapor sterilization. Study n. 3 The purpose of the study was to determine the temperature at which the human scent is degraded so that a dog would not be able to identify it. In contrast to expectations, eight dogs used in the experiment almost flawlessly identified human scents from five scent donors exposed to temperatures of 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, and 800°C. Only two of the dogs were able to identify 5 of 15 scent samples exposed to 900°C. No dog identified a scent exposed to 1000°C. Our study verified heat survivability of human scent far beyond existing expectations. Study n. 4 We tested the hypothesis that if odor fallout (the release of a human odor onto an untouched object) in human subjects exists, then holding a hand above an absorbent will produce a detectable scent which will be subsequently matched in a detection test by trained dogs. Scents were collected from seven males to sterile cotton absorbent squares. The left hand was used to get the control scent and the right hand served as the target scent. Each experimental subject was sitting and his left hand was laid down on a cotton square for 3 min. The right hand was held 5 cm above another cotton square for 3 min. The scent identification was done by two specially trained police German shepherds. Both dogs performed 14 line-ups and correctly matched the collected scents of all test subjects. The results suggest the existence of human odor fallout, whereby a human scent trace is left by humans even if they do not touch an object.

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