Photometric measurement of pressure-induced blanching of livor mortis as an aid to estimating time of death. Application of a new system for quantifying pressure-induced blanching in lividity.

A newly developed digital system employs photometric measurement of pressure-induced blanching of livor mortis to estimate time of death. The conventional method of applying pressure with thumb or forceps relies largely on subjective interpretation. Our system improves on this method by photometric quantification of color changes produced by defined magnitudes of pressure. We tested the new system by applying increasing levels of pressure to lividity in 50 cadavers with known time of death. Characteristics courses for pressure-induced changes were found for the brightness component of livor mortis, revealing distinct differences between the respective postmortem intervals. The surface areas under these curves were then calculated and distributed into 10-hour postmortem time categories. Variance analysis of these surface values revealed clear differences between the time categories, especially in the medians. Distinct differences between the various postmortem time categories were also evident for the chroma component of livor mortis. The new system offers a further method--in addition to body temperature, rigor mortis, and the electrical responsiveness of skeletal muscles--for estimating time of death, especially after long postmortem intervals.