Effects of rounding errors on postmortem temperature measurements caused by thermometer resolution

Abstract

Beginning 7 h after death, a datalogger was used to measure the temperature in the external auditory canal of an adult male body placed in a refrigerated room. The sequence of measured values approximated a single exponential function with a correlation coefficient of 0.998475. This suggests that the starting time of body cooling in the refrigerated room under constant temperature can be calculated with less error using any two data points recorded by the datalogger. However, the results of such calculations varied widely and longer postmortem intervals demonstrated greater calculation errors. Periodic errors also appeared. Mathematical simulations showed that this variation was caused by rounding errors, which represent the difference between the thermometer readings and the true temperature. The resolution of the thermometer was 0.1 degrees C, a normal specification; however, even this led to noticeable rounding errors. Therefore, significant errors may influence postmortem interval estimations using other body temperatures. When body temperatures are used to determine the time of death, a method that minimizes rounding errors should be considered.

Influence of measurement errors on temperature-based death time determination

“…The fact that only few studies have dealt with that problem so far (e.g., [2]) has to be attributed to numerous difficulties inherent in the subject. Experimental approaches need much organizational effort, are expensive, and compromised by ethical problems.…”

“…In the study [2], the authors used a Newtonian model (which is a simple exponential approach to body cooling) and applied it to the temperature of the external auditory canal of a body cooling under controlled conditions in a refrigerated room of 4°C. They investigated the errors in death time back-calculation based on their model given (a) two temperature-time points with a time difference of 30 min or, alternatively, (b) 30 temperature-time points with a time difference of 1 min between each pair of two successive points and found that the rounding errors caused by a thermometer resolution of 0.…”

“…Kanawaku et al [2] studied the effects of rounding errors on postmortem temperature measurements in the external auditory canal caused by thermometer resolution. Other groups compared real cases with exactly known death times to determine the precision of numerical death time estimation models [3][4][5][6][7][8][9][10][11][12][13].…”

Body mass and corrective factor: impact on temperature-based death time estimation

“…Kanawaku et al [16] studied the effects of rounding errors on post-mortem temperature measurements in the external auditory canal caused by thermometer resolution. Other groups compared real cases with exactly known death times to determine the precision of numerical death time estimation models [1,4,[10][11][12][13][14][17][18][19].…”

“…12 13 15 16 17 19 20 21 23 24 25 27 28 29 31 32 33 35 36 37 39 40 41 43 44 Time since death [h] Climatic chamber cooling experiment. Temperatures: measured T(t); environmental T E (t); and Henssge with correction factor c 0 =1.0: T H0 (t); c 1 =1.1: T H1 (t); c 2 =1.2: T H2 (t); c 3 =1.3: T H3 (t)…”