This report describes a research project that has direct impact on forensic investigations, with details on the impacts that common coatings and residues from surfaces have on bloodstains and fluid dynamics.
This document reports on a research project aimed primarily at collecting data on which common coatings and residues, which are often invisible to the eye, can dramatically alter the shape and size of bloodstains. The researchers’ secondary goals were to investigate 3D morphological features to determine if they contained the necessary information for detecting the presence of the residues, and to generate extensive photographic data of human blood-drop impact and drying under various conditions so that a fundamental understanding of the underlying fluid dynamics could be pursued. The two major research questions addressed by this research project were: how the advancing and receding contact angles might affect the bloodstain size, and if those angles are influenced by hematocrit; and if there is a difference between oblique and inclined impact on a blood stain pattern. The report describes the research design, methodology, and analytical data analysis techniques. The results demonstrate that bloodstains from drops on low adhesion and oily surfaces can be fundamentally different from those on cleaned surfaces, and if the drop can recoil or shrink after it has impacted the surface, it can be miscategorized as a non-drip drop.