Transfer of Bloodstains from Textile Surfaces: A Fundamental Analysis

As submitted by the proposer: Bloodstains may transfer from one surface to another, for example from a bloodied textile to another textile, such as when a family member returns home and finds their loved ones bloodied. In attempting to render assistance they may transfer blood to their clothing from the victims clothing. On the other hand, the family member may also be a suspect. Currently, there are no definitive studies of transfer stains from one textile to another. One difficulty in performing rigorous studies of transfer stains to or from textiles is the inconsistency of blood from one person to another. This requires studies with blood from several people or animals, with the added health risks and disposal. Currently, no synthetic blood exists that is adequate for forensics. To address these issues, there are two major goals of the proposed research: (1) to provide a fundamental understanding of blood transfer from one textile material to another (Swgstain research need #2) and (2) to develop a synthetic blood that closely mimics the properties and behavior of human blood (Swgstain research needs #8). The dependence of transfer stains on the drop volume, the fabric that blood first contacted, the fabric that the blood was transferred to, the time between first impact and transfer, and the contact pressure between the two fabrics during transfer will be determined for transfers between plain woven and knit fabrics. The quantity of transferred blood and the transferred pattern will be determined and related to the properties of blood (e.g. red blood cells, viscosity, surface tension) and textile engineering construction factors of the fabric. This research will require hundreds of samples, which renders the use of human or animal blood impractical. Therefore, a new synthetic blood will be developed that has the correct surface tension and hematocrit, while closely mimicking the non-Newtonian viscosity of real blood. It will contain polymeric particles that have correct size, shape, surface charge, and color as red blood cells. Bloodstains using this synthetic blood will be compared to stains formed in the same way using pigs blood. The key deliverables of this study will be a new, forensically meaningful synthetic blood and fundamental understanding of the science behind blood transfer between the most common woven and knit apparel fabrics along with quantitative models to predict the transfer behavior of blood between these fabrics. ca/ncf