Human odor can be differentiated among individuals and can therefore be seen as a biometric that can be used to identify this person. Dogs have been trained to identify objects held by a specific person for forensic purposes from the beginning of the twentieth century. Advancing technology has made it possible to identify humans based on headspace analysis of objects they have handled, opening the route to the use of odor as a biometric.
From the early twentieth century, dogs have been used to find and identify humans based on their odor. This has originated from the capacity of dogs to follow the track of a person, either by following the odor the person left directly on the ground that the dog needed to follow quite closely (“tracking”), or by following a broader odor trail that the dogs could follow at some distance (“trailing”). Some dogs were very “track-sure”: i.e., they continued to...