NCJ Number
249851
Date Published
April 2016
Length
54 pages
Annotation
This project conducted fundamental and collaborative research on the formation of bloodstains, leading to the delivery of a knowledge base, innovative measurement methods, and pieces of open-source analysis software to assist bloodstain pattern analysts in determining how a violent crime was committed.
Abstract
A method for trajectory reconstruction was developed, based on the reconstruction of curved trajectories by estimating impact conditions from three-dimensional measurements of stains. Based on a set of laboratory experiments analogous to the situation created by a beating, the method was found to be approximately four times more accurate than the method of using strings to determine the region of origin of a blood spatter. The device used to inspect stains in 3D has been modified to be portable; however, the method currently provides accurate measurement of the shape and minute volume of stains only when they are on smooth and non-absorbing surfaces. In addition, because it is important to know the physical properties of the blood, this project conducted measurements of the physical properties of porcine blood, which is a valid substitute for human blood. Measurements were performed at both equilibrium conditions and in dynamic situations that approximated those in blood pattern analysis. A set of innovative and simple tools is proposed for characterizing blood properties, such as shear-thinning viscosity or the relation between drop spreading upon impact and impact conditions. A numerical simulation tool was also developed to describe the impact of blood drops, with specific consideration of the role of "wettability." In addition, the project published a review of the relations between fluid dynamics and bloodstain pattern analysis, so as to link these fields of expertise, as recently recommended by the National Academies. 32 figures and 57 references