Microscopic imaging of human bloodstains: testing the potential of a confocal laser scanning microscope as an alternative to SEMs.

The forensic interest on human bloodstains derives from their relation to crime investigation, whereas an archaeological and ethnographic concern arises from their occurrence because of warfare and ritual. The development of digital reflected light microscopes provided an opportunity to use ligh microscopy to study surface topographies in a more accurate way than previously. However, this enhancement has been focused on increasing magnification rather than resolution. An advanced type of light microscope is the confocal laser scanning microscope (CLSM). Its potential as an alternative to scanning electron microscopes (SEMs) for imaging human bloodstains was tested. A fragment of stone (brown chert) was smeared with human peripheral blood, air-dried, and stored indoors. After nearly two years, the sample was examined and imaged using an Olympus LEXT OLS4000 CLSM. The surface detail of CLSM images appeared to be comparatively lower than that of SEM micrographs of coated bloodstains taken at high-vacuum mode and high accelerating voltage, similar to that of SEM micrographs of uncoated bloodstains taken at low-vacuum mode and high accelerating voltage, and similar to or even higher than that of SEM micrographs of uncoated bloodstains taken at high-vacuum mode and low accelerating voltage. These results suggest that a CLSM is a practical alternative to SEMs for imaging human bloodstains when a very-high level of surface detail is not required.