Cadaver dogs: unscientific myth or reliable biological devices?

Dogs are commonly used to detect explosives, narcotics, and other illegal materials. In the forensic setting, cadaver dogs are trained to detect and locate concealed human remains or fluids due to the high sensitivity and selectivity of the canine olfactory system and the relative ease with which dogs can be trained and handled. The need for international and scientifically validated standards has long been outlined by the literature. It is important, therefore, to establish the reliability of the handler/dog team. Our study aimed to detect the real effectiveness of dogs trained to locate human cadaveric blood in very low concentrations, through an optimized and rigorously controlled design which would rule out any possible sources of bias. The study was designed to determine the dogs' olfactory sensitivity to human cadaveric blood and how this capacity might change as the dilution of blood increases from pure blood to very low concentrations. The further step was to examine the dogs' ability to discriminate among target (human cadaveric blood) and non-target (confounding substances) odors (discriminative capability). Our results revealed that well trained dogs were able to detect human cadaveric blood samples even when very low concentrations of blood were stored in the tubes, showing high levels of olfactory sensitivity and to discriminate the target odor even when the non-target odor was orders of magnitude higher in concentrations. Although our results are based only on two dogs, the procedure we used may provide a comprehensive answer to the need for a scientifically unassailable tool for quantifying and objectifying the performance of well-trained specific search dogs in detecting human cadaveric blood traces.