Spectrophotometric and tristimulus analysis of the colors of subcutaneous bleeding in living persons.

In forensic activities the estimation of the age of subcutaneous bleeding is very important. The evaluation of color, however, will vary according to differences of light-source, observer, size, background and so forth. The colorimetric methods using a spectrophotometer can effectively evaluate skin discoloration. In this study, the tristimulus and spectrophotometric patterns of color changes of skin bruises were examined among eight Japanese adult men volunteers wounded by a sharp pinch on the inside of the upper arm and forearm. From a series of color changes among the subjects, the tristimulus data and the spectral reflectance graphs showed variable patterns that made a comparison of absolute numerical values by a single measurement meaningless. Therefore, if we use colorimetric methods in a practical case, we should measure bruises in the same lesion twice or more at intervals of 1 or 2 days.