Evaluating the Accuracy of Bloodstain Pattern Analysis Using Hemodynamic Factors

Abstract

This comparative survey explores the relationship between the discipline of bloodstain pattern analysis (BPA) and hemodynamic blood properties, such as viscosity and hematocrit. In BPA, forensic scientists study the phase change of blood when in contact with air, but little forensic literature connects blood biomechanics, such as hematocrit levels, to BPA. Red blood cell count, or hematocrit, in females (37-48% of blood volume) is slightly lower than males (45-52% of blood volume) from menstrual red blood cell loss, etc. Strong evidence suggests that erythrocytes influence blood viscosity because of their high concentration (4-6 x 106 RBC/mm3 or 40-45% of blood volume in healthy individuals). When whole blood is altered by a disorder/disease or alcohol intake, hematocrit levels can be affected as well. With this knowledge, there is reason to believe that blood viscosity changes with individualistic hematocrit levels. Therefore, it is hypothesized that traditional BPA can produce inaccurate results. Intravenous blood samples were drawn from nine volunteers (all women, including eight with blood alterations and one healthy control) into collection tubes containing ethylenediaminetetraacetic acid. Each sample was tested for viscosity using a Cannon-Fenske viscometer and hematocrit levels using a ZipCombo centrifuge. Each sample was used to make several bloodstains at varying degrees of impact (10, 30, 60, and 90). ANOVA (α = 0.05) and Tukey HSD statistics were used to compare angle of impact variables against each other within the nine participants. This survey connects hemodynamic properties to angle of impact tests in BPA by significantly showing how bloodstains can be misinterpreted. By examining blood viscosity among several individuals, this research assesses the accuracy of BPA by comparing experimental and expected bloodstain angles and creates a predictive framework for analyzing bloodstains created by physiologically altered blood. In conclusion, hemodynamic factors among individuals were found to influence traditional BPA methodology and future research is recommended to better understand hemodynamic properties and fulfill the recommendations made by the 2009 National Academy of Sciences (NAS) Report.