Experimental bloodstains on fabric from contact and from droplets

The differentiation between contact bloodstains and stains produced by projected droplets on fabric can be crucial in crime scene reconstruction since suspects can explain bloodstains on their clothing by contact with the victim post mortem. Experimental smear and contact pressure stains on three different types of fabric were compared with stains produced by falling and projected droplets ("dynamic" stains) of equivalent size. The morphology of the small stains (0.1-10 microliters) was investigated with a macroscope. Characteristic for "dynamic" stains are symmetry and rhythmicity (secondary droplets) of the stain and a zonal drying pattern. Contact stains lack the characteristic features of "dynamic" stains and show a clear impregnation of the material resulting in a blood-soaked reverse side of cambric and cotton and in a paler overall colour. The mode of formation of microstains (blood volume 1 < microliter) on irregular surfaces (e.g. terry cloth) can be difficult to determine since the rough surface structure and the small blood volume reduce the characteristics of dynamic stains. In these cases, comparison with experimental stains on the same surface material is recommended.