Influence of the ear temperature range on the measurement bias between an infrared thermometer and a reference probe for post-mortem interval determination.

The aim of this study was to assess the influence of the post-mortem outer ear temperature (OET) on the measurement bias previously observed for short post-mortem intervals (PMI) between a commercially available infrared thermometer and a reference metal probe thermometer. To that end, 100 refrigerated bodies were added to our initial cohort to investigate lower OET. In contrast to our previous findings, a very good concordance was noted between both methods. There was still an overall underestimation of ear temperatures with the infrared thermometer, but the average bias was significantly reduced compared to that observed in the initial cohort (1.47 °C for the right ear and 1.32 °C for the left ear). Most importantly, this bias progressively decreased as the OET decreased, becoming negligible for OET lower than 20 °C. These results are in agreement with literature data regarding these temperature ranges. The discrepancy observed with our previous observations may be due to the technical characteristics of the infrared thermometers. The lower the temperatures measured, the more the measurements approach the lower limit of the measuring range of the device and tend to give constant values, resulting in a smaller underestimation of the measurements. Further research is needed to assess the interest of integrating in the already validated OET-based formulae a variable dependent on the temperature measured with the infrared thermometer, to eventually allow infrared thermometry to be used for PMI estimation in forensic practice.

Estimation of the time since death based on body cooling: a comparative study of four temperature-based methods.

The estimation of the time since death is an important task in forensic medicine that mainly relies on body cooling in the early post-mortem period. The rectum has been traditionally used to determine the central core temperature after death, though the external auditory canal has been proposed as an alternative site by several authors. The objective of this study was to assess the ability of four body temperature-based methods (Henssge's rectal nomogram, Henssge's brain nomogram, and Baccino's both interval and global formulae based on ear temperature) to estimate the post-mortem interval (PMI). PMI calculations were carried out based on ear and rectal temperature measurements performed with a reference metal probe on 100 inpatient bodies with an average PMI of 4.5 ± 2.5 h. For practical purposes, ear temperature measurements were applied to Henssge's brain nomogram. All methods could be applied to 81 cases, since high body temperatures prevented the rectal nomogram method from being used in most of the remaining cases. The actual PMI was within the time interval (95% CI) provided by the rectal nomogram method in 72.8% of cases, and in 63.0% to 76.5% of cases when using ear temperature-based methods. The proportions of adequate estimates did not differ statistically between the different methods. When the methods failed to provide a reliable time interval, all except the brain nomogram tended to underestimate the PMI. Similar results were obtained in the subgroup of normothermic patients at the time of death (n = 63), confirming that the PMI calculations had not been biased by the inclusion of patients with thermoregulation disorders. Our findings are in accordance with the published literature which suggests that ear temperature-based methods are as reliable as those based on rectal temperature for estimating the early PMI and that they may be used as quick, simple, and non-invasive methods at the scene, although caution should be taken in interpreting their results given their high error rates. However, further research including field studies is recommended to confirm their practical relevance in forensic casework.

Is infrared thermometry suitable for the determination of the time since death based on ear temperature? A comparative study of two measurement methods.

Infrared thermometry has been proposed as an interesting alternative to probe thermometers for recording ear temperature in cadavers to estimate the postmortem interval (PMI), but it has still to be validated in this setting. Our objective was to compare the performance of an infrared thermometer to that of a reference probe thermometer for measuring ear temperature. Temperature measurements were performed on 100 cadavers (mean PMI: 4.5 ± 2.5 h) using the infrared and the probe thermometers. The repeatability of the measurements, their correlation, and the agreement between both methods were evaluated. We showed a good repeatability of the measurements with the infrared thermometer (Lin's concordance correlation coefficient (CCC) = 0.93 [0.72;0.98] for the right ear; CCC = 0.94 [0.75;0.98] for the left ear), and there was a strong and significant correlation between measurements provided by the two instruments (p < 0.001). However, a poor agreement was found between both methods, with a systematic underestimation of about 2 °C of the ear temperature when measured with the infrared thermometer. Data from auricular infrared thermometry should not be applied to algorithms developed for probe thermometers to estimate the PMI. Further research is needed to develop a reliable algorithm specifically based on infrared thermometry.