The intent of this study was to attempt to quantify error associated with the measurements required in area of origin reconstructions resulting from the analysis of blunt force impact patterns. Mathematical tables were constructed in order to examine trends associated with changing width and length ratios and the influence of impact angle change and area of convergence deviations. The analysis of the trends enabled informed stain selection, mitigating potential error. The analysis of the influence of stain measurement error and gamma angle error was conducted by reconstructing experimentally created blunt force impact patterns using the Tangent Method, comparing the resulting area of origin determinations to reconstructions generated using HemoSpat, a bloodstain pattern analysis software, and then isolating each variable in order to examine its effect on precision and accuracy.
A total of 10 blunt force impact patterns were created and initially analyzed utilizing the Tangent Method. The stains selected for the analysis of each pattern were input into HemoSpat software which generated separate and independent results, enabling a comparison of the absolute and relative error rates between the known area of origin and the two methodologies. This also provided a foundation for the examination of each variable’s contribution to absolute and relative error. Finally, artificially induced measurement error was generated by uniformly increasing and decreasing the length, width, and gamma angle values of the selected stains based on an absolute analysis of error. The deviation from the compared values was examined in order to determine if the resulting area of origin determination would adversely affect inferences related to scene analysis. The results indicate that the incorporation of measurement error into a reconstruction creates an error rate that would not substantively affect an area of origin determination or inferences which would typically be rendered based on that determination.