Verification of the exponential model of body temperature decrease after death in pigs

Abstract

The authors have conducted a systematic study in pigs to verify the models of post-mortem body temperature decrease currently employed in forensic medicine. Twenty-four hour automatic temperature recordings were performed in four body sites starting 1.25 h after pig killing in an industrial slaughterhouse under typical environmental conditions (19.5-22.5• C). The animals had been randomly selected under a regular manufacturing process. The temperature decrease time plots drawn starting 75 min after death for the eyeball, the orbit soft tissues, the rectum and muscle tissue were found to fit the single-exponential thermodynamic model originally proposed by H. Rainy in 1868. In view of the actual intersubject variability, the addition of a second exponential term to the model was demonstrated to be statistically insignificant. Therefore, the two-exponential model for death time estimation frequently recommended in the forensic medicine literature, even if theoretically substantiated for individual test cases, provides no advantage as regards the reliability of estimation in an actual case. The improvement of the precision of time of death estimation by the reconstruction of an individual curve on the basis of two dead body temperature measurements taken 1 h apart or taken continuously for a longer time (about 4 h), has also been proved incorrect. It was demonstrated that the reported increase of precision of time of death estimation due to use of a multiexponential model, with individual exponential terms to account for the cooling rate of the specific body sites separately, is artifactual. The results of this study support the use of the eyeball and/or the orbit soft tissues as temperature measuring sites at times shortly after death. A single-exponential model applied to the eyeball cooling has been shown to provide a very precise estimation of the time of death up to approximately 13 h after death. For the period thereafter, a better estimation of the time of death is obtained from temperature data collected from the muscles or the rectum.

First practical applications of eye temperature measurements for estimation of the time of death in casework. Report of three cases

“…The corneal temperature is in fact the surface eye temperature, but can to some extent influence internal eyeball temperature, however the retinal temperature is affected by less than 1.8 8C during an ambient temperature change from À20 8C to +40 8C [10]. The slightly lower (around 1 8C) initial eyeball temperature compared to the core body temperature was also confirmed in pigs [7].…”

“…The mean value of k c = À0.113 h À1 was determined in studies on pigs eyeballs postmortem cooling process in room temperature 18-22 8C and still air [7][8][9]. Transformation of Eq.…”

“…During the studies on a number of pigs killed straight before the commencement of several-hours long postmortem eye temperature recording, the mathematical formula allowing for calculate the TOD was designed [7][8][9]. A good precision of TOD estimation, especially in the initial postmortem period, can be obtained due to the lack of or only residual plateau effect in this body site [1,[7][8][9]. …”

Post-Mortem Estimation of Time of Death of Dogs Based on Measurements of Kidney Temperature in Comparison with Rectal Temperature

“…The research confi rmed the lack of a plateau effect. It was established that in the case of the use of the eyeball the most reliable results can be obtained during the period up to 13 h after death, whereas in the case of the temperature of the orbital soft tissues the greatest precision is obtained up to 10.5 h after death [31]. This study also found no plateau in the decrease in temperature in the case of the orbital tissues and eyeballs.…”

Techniques to reduce the temperature of beef muscle early in the post mortem period – a review

“…Typically the rate of change in temperature varies with time from death and can be described as a monotonic exponential decay for superficial muscles and a sigmoid shape decay for deep muscles in large carcasses (Kaliszan et al 2005). For the latter, the period of temperature inertia at the beginning of the post mortem period is likely due to; (i) metabolic heat production that continues for several hours post mortem and (ii) meat having a relatively low thermal conductivity coefficient that limits the rate of heat movement from within a muscle to the surface.…”