3D morphology of blood stain can provide critical information missed in standard bloodstain analysis

Bloodstain Pattern Analysis (BPA) is a vital tool in reconstructing crime scenes in which bloodletting occurs. The area of origin of a bloodshed event is typically determined from the length, width, and orientation from a selection of bloodstains. Experiments suggests that these parameters can depend on the substrate material, and even invisible coatings on these materials can fundamentally change the appearance of a bloodstain. Yet the underlying mechanisms are not well understood, nor are there readably available tools characterize the wetting properties of the substrate at a crime scene. This proposal aims to first develop the fundamental understanding needed to characterize these critical substrate-blood interactions missed in the standard BPA approach and then to identify how this information can be deconstructed from the 3D morphology of the blood stain and be readily obtained from appropriately-taken crime-scene photographs. Thus the aims in this proposal are directly relevant to the practice and theory of Bloodstain Pattern Analysis.

The research documents the spreading and drying patterns of human blood on carefully controlled surfaces. Unlike previous studies that have focused on clean, bare surfaces, the proposed work will focus on smooth surfaces with common residues and microscopic coatings that will be systematically applied and characterized. Individual blood drops will be directed to the surface and measured with multiple high-speed and time-lapse cameras. The 3D stain morphology will be obtained from photographs for varying impact conditions (drop size, impact velocity and impact angle, coagulation rate) and target conditions (coating, substrate, and inclination angle) over periods of milliseconds to hours.

There are three hypotheses that will be tested in this research. First, certain coatings will de-pin the contact line and significantly modify the shape of the bloodstain over various timescales. Second, the inclined and oblique impact may not be equivalent on these coatings. Third, substrate-drop interactions will be encoded in the 3D morphology of the blood stain. If the hypotheses are correct, there will be a clear path to further reduce the uncertainty of the area of origin in a spatter. No subjects are used in this study. The results will be submitted to forensic and fluid dynamic peer-reviewed journals, as well as disseminated in conference presentations and Bloodstain Pattern Analysis working groups. Note: This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14). CA/NCF