On the issue of choosing the accuracy of a temperature meter when determining of the time since death using the thermal method

Justification: To date, the thermometric method for determining TSD has not established what accuracy of temperature measurement is satisfactory from the point of view of the requirements of forensic medical examination practice.

Objective of the work: Creating practical recommendations for choosing the instrumentation used in the process of expert examination of a dead body, based on a study of the effect of the instrumental accuracy of measuring the temperatures of a corpse and the environment on the magnitude of the error in determining TSD of a person by calculation.

Methods: Based on the phenomenological mathematical model of C. Henssge, the dynamics of body temperature in various diagnostic zones (brain, liver, rectum) was simulated at ambient temperatures of 0°C and 20°C, and for the specified external conditions, the instrumental error of the method was calculated for thermometers with different measurement accuracies - 1°C, 0.1°C, 0.01°C. The instrumental error was expressed both as an absolute value and as a relative value (%) - as a ratio to the TSD value at which it was obtained.

Results: It was found that the highest values ​​of the relative error are recorded at the initial stage of body cooling and at the stage of equalization of the temperatures of the body and the environment. At the same time, in all cases, the use of thermometers with a temperature measurement accuracy of 1°C was accompanied by the formation of a relative error exceeding 15% of the TSD value. At the same time, the use of devices measuring temperature with an error of 0.1°C and 0.01°C made it possible to achieve a relative instrumental error of no more than 5% throughout the entire modeling period (2-24 hours).

Conclusion: From the point of view of the requirements established for medical and biological research, a satisfactory result is fundamentally possible only in cases of fixing the temperatures of the corpse and the environment with an accuracy of 0.1° or 0.01°C. For ease of practical use, the authors have implemented an algorithm for calculating the instrumental error of determining the DNS in the form of a Microsoft Excel calculation sheet.