Spectrophotometric evaluation of the colour of intra- and subcutaneous bruises.

Spectrophotometric measurements were performed on intra- and/or subcutaneous bruises occurring in direct temporal connection with peracute fatal trauma. The purpose of these measurements was to determine whether the visual colour impression of a fresh traumatic extravasation can give information on the localisation of the haemorrhage in a certain tissue layer. After visual assessment of the colour of the bruise, the spectral reflectance curves and the CIE-L*a*b* colour values were determined with the help of a diode array spectrophotometer. The localisation and size of the haemorrhages in the cutis and/or subcutis were evaluated morphologically after incision of the skin. It was confirmed that there is a relationship between the colour impression and the localisation of the bruise. Bruises localised near the surface have a more reddish appearance while bruises in deeper layers give a more bluish colour impression. An explanation may be found in the optical characteristics of skin. Blood localised in the subcutis appears blue on the surface due to scattering processes in the dermis (Rayleigh scattering), as the blue wavelengths of the light are scattered (and thus reflected) to a greater extent than the red wavelengths.