Predictive equation for post-mortem interval using spectrophotometric values of post-mortem lividity: A pilot study

Abstract

The colour of post-mortem lividity and control skin of 86 cadavers was measured spectrophotometrically to obtain L^* (value), a^* (chroma) and b^* (hue) values. In addition, left heart blood (n = 58), right heart blood (n = 57) and blood from the femoral vein (n = 21) were measured. Using these data, we analysed the relationship between post-mortem lividity, control skin and blood colours. L^* of post-mortem lividity (L^*_p) and control skin (L^*_c) were strongly correlated ( r = 0.64). a^* and b^* of post-mortem lividity (a^*_p and b^*_p) significantly increased with an increasing post-mortem interval (PMI) but r² values were low (0.11 and 0.070, respectively). Predictive equations for post-mortem lividity colour (L^*_p, a^*_p and b^*_p) were developed using control skin colour (L^*_c, a^*_c and b^*_c) and autopsy findings for the first time. The predictive equation for L^*_p explained almost 65% of the observed L^*_p. We created predictive equations for PMI with and without blood colour values, and the most accurate equation, which did not use blood colour values, made it possible to estimate PMI within ± 10.29 h. Further study of these equations will help us to understand the factors that affect post-mortem lividity colour and increase the accuracy of equations for predicting post-mortem lividity colour and PMI.

Keywords: Blood colour; Post-mortem interval; Post-mortem lividity; Skin colour; Spectrophotometry.