Authors: Andrea Celeste Medrano1* BS; Chris Holleyman MA2, and Paola A. Prada-Tiedemann1, Ph.D.

1Forensic Analytical Chemistry and Odor Profiling Laboratory, Department of Environmental Toxicology, Texas Tech University, Lubbock, TX; 2Sirius Metrics, Inc., a 501(c)(3) organization, Burtonsville, MD

Dogs are known to be a man’s best friend, but what is often overlooked are the capabilities that these animals possess when it comes to odor detection. The utilization of canines as a biological detector tool has increased immensely as they now assist various law enforcement agencies to locate a wide variety of target substances.
Human remains detector (HRD) canines—also commonly referred to as cadaver dogs—are an evolved specialty from the search and recovery discipline and have become a crucial tool for victim recovery efforts around the globe. These biological sensors are trained to locate human remains in the form of whole bodies, body parts, blood, bone, tissue, or decomposition fluids. To maintain the canine team at optimal performance and ready for deployment scenarios, handlers use training aids across the decomposition spectrum of putrefaction to maintain training regimens year-round. Therefore, a range of training aids are utilized—including human dry and wet bone, blood, decomposition liquids, adipocere, to name a few.
During the complex process of decomposition, different microorganisms, including bacteria and fungi, play a role in tissue breakdown within the body. This breakdown releases various liquids, gases, and chemical compounds, yielding the release of volatile organic compounds (VOCs). There has been a renaissance of research studies to identify types and amounts of distinctive compounds under different environmental conditions and decomposition stages from both human and animal models. However, a current gap in the literature is understanding how this decomposition odor profile affects canine training as a function of routine training aid use. Hence, the objective of this study was to collect samples at different stages of decomposition and monitor the stability of the instrumental odor profile across a period of six weeks under refrigerated conditions.
The present study used nine animal models (Sus scrofa) with a focus on three decomposition stages (fresh, advanced decay, skeletal) for tissue and/or bone sample collection during three distinctive sampling seasons (summer, fall, and winter of 2021-2022). Once the targeted stage had been reached, tissue samples were collected, stored, and analyzed via Solid Phase Microextraction-Gas Chromatography/Mass Spectrometry (SPME-GC/MS). The headspace odor concentration of each simulated-training aid was monitored over a 6-week period to evaluate compound frequency and occurrence. “Continuous” samples were repeatedly thawed/frozen each week to simulate routine training aid handling. In addition, a set of triplicate samples for each week were analyzed once throughout the 6-week period, which would represent the “preserved” samples in this study. This would not only allow for the determination of any odor profile degradation caused by continuous use, but to additionally see if preserved training aids would depict a more stable chemical odor profile over an extended period of time. The results depicted a difference in chemical compound abundance within the different stages of decomposition, as well as the different environmental seasons. Statistical analysis of the odor profiles at each week showed that the continuous samples had overall higher correlation ranks than the preserved samples. This suggests that the continuous samples maintained the baseline VOC profile more effectively than the preserved samples. This result suggests that a continuous thaw/refrigeration cycle does not equate to a degradation of odor availability. Concurrently, the samples that were under prolonged refrigeration until the tested week depicted a loss of odor availability thereby suggesting the need for longer thaw cycles to capture the sample odor baseline measurements. This longitudinal study provides a pathway to understanding the chemical odor profile stability under refrigerated conditions for simulated decomposition training aids and provide canine trainers chemical-based information as to the odor fate of target odor sources.