An Impact Velocity Device Design for Blood Spatter Pattern Generation with Considerations for High‐Speed Video Analysis,

A mechanical device that uses gravitational and spring compression forces to create spatter patterns of known impact velocities is presented and discussed. The custom‐made device uses either two or four springs (k₁ = 267.8 N/m, k₂ = 535.5 N/m) in parallel to create seventeen reproducible impact velocities between 2.1 and 4.0 m/s. The impactor is held at several known spring extensions using an electromagnet. Trigger inputs to the high‐speed video camera allow the user to control the magnet's release while capturing video footage simultaneously. A polycarbonate base is used to allow for simultaneous monitoring of the side and bottom views of the impact event. Twenty‐four patterns were created across the impact velocity range and analyzed using HemoSpat. Area of origin estimations fell within an acceptable range (ΔX_av = ?5.5 ± 1.9 cm, ΔY_av = ?2.6 ± 2.8 cm, ΔZ_av = +5.5 ± 3.8 cm), supporting distribution analysis for the use in research or bloodstain pattern training. This work provides a framework for those interested in developing a robust impact device.