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

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.