Cooling of the Carcases for Veterinary Medico Legal Use

Animals were euthanized at the internal clinic of the University of Veterinary Medicine and Pharmacy (UVMP) in Košice because of old age or incurable disease which would cause suffering and pain to survivors. The decrease in body temperature was measured by a special thermometer, with one probe inserted in the animal rectum and the other used for measurement of ambient temperature (Figure 1). The initial 10 min measuring interval proved to be insufficient so we used 30 min interval to obtain one temperature recording (until the temperature of cadaver dropped to ambient level) (Table 1) (Figure 1).

Our observations proved that the main factors influencing the course of cooling are the animal weight and the temperature of the environment where the cadaver was located. According to the general rule, animal cadavers cool at the rate of 0.6 – 0.8°C per hour, though this does not consider all factors influencing the cooling, e.g. air flow which can speed up the cooling or immersion in water causing 3-fold faster cooling. In our experiment we recorded the fastest cooling of cadavers in group 2 (1.2°C within the first 4 hours). Cadavers from group 1 cooled at a rate of 2.5°C/hour, those from group 3 at a rate of 2.4°C/hour on average, and cadaver from group 7 (body weight 56 kg, placed outside in winter) cooled within the first hours at a rate of 1.7°C/hour.

Figure 1: Measuring of the body temperature by using of thermometer Testo 175 T3

The temperature drop 2.8°C /hour was recorded in cadavers from group 4, which were exposed to air flow. The cadavers from group 6 exposed to conditions which imitated drowning cooled at a rate of 4oC/hour during the first hours of cooling. After 15 hours, the temperature decrease has stabilised in individual groups and reached the rate of 0.7 – 0.5°C/hour. We recorded also occurrence of the so-called plateau phases (several hours without drop of temperature), but in time intervals differing from those recorded in human corpses. The plateau phase was followed by a decline (0.3 – 0.2°C/ hour). During the last hours of cooling, the cadavers cooled at a rate of about 0.1°C until the temperature of both the cadaver and environment became equal which occurred within 27 – 117 hours. When comparing with the results obtained by human forensic pathologists, the temperature measured in the rectum drops very slightly or not at all for about half an hour after death (post mortem temperature plateau). This is followed by a linear rate of cooling (between 0.5 to 1°C per hour) for the next 12 to 16 hours. Then the cooling rate is relatively uniform in its slope. Then it gradually becomes slower, and when the temperature is within about 4°C of the environment, rate of algor mortis cooling becomes very slow (Algor Mortis, 2012).

Comparison of the values presented in (Table 2) shows that the rate of cadaver cooling is affected by both the carcass weight and the environmental conditions to which the cadaver was exposed. We observed that the temperature dropwas slower in cadavers with higher weight. This indicates that the rule determining the cooling rates of cadavers equal to 0.6 to 0.8°C per hour is very general. Information obtained from crime scene are useful for establishing the

Table 2: Decline of body temperature in hours in each group separately

Figure 2:Time of death

time of death (Figure 2). The values determined in this study will be used to draw nomograms for later use by veterinarians when performing reconnaissance as well as for procuring the grounds for determining the time of animal´s death.

Establishing an accurate and precise TOD persist as the holy grail of forensic pathology, despite decades of research. Determining time of death is a constantly evolving research area. In summary, the amount of information available for determining TOD in veterinary species is extremely limited. Given the limited amount of information, as well as the persistently imperfect and inexact science of time of death determination, currently veterinary pathologists may be as well served by personal experience as by sophisticated rectal probes (Gerdin and McDonough, 2013). Potentially pertinent information may be gleaned from some human research based on animal models such as decompositional scoring. Veterinary forensic pathologists should strongly consider documenting and developing a database of known decomposition findings associated with known environmental conditions in their area based on all necropsies performed, not just forensic (Merck, 2014).

Gabriela Vargova carried out the experiments and wrote the draft of manuscript. Daniela Takáčová checked the experimental design and supported in English writing manuscript.

The authors have no conflict of interests.

Our thanks goes to the staff of the Clinic of the Small Animals (Internal clinc), as well as owners of pets that were left them at clinic for making our experiments.