Impact of blood droplets

Within Bloodstain Pattern Analysis, forensic experts commonly use the stringing method, based on a straight line approximation of the blood droplets trajectories to determine where the source of a bloodstain pattern was. However, by ignoring gravity, large errors may arise when inferring the 3D-location of the wound, making it impossible to discern, for example, between a standing and sitting position. To reconstruct the trajectories correctly, the impact velocity of the droplets is required. In this thesis it is shown how this can be done directly from the shape and volume of dried bloodstains. By using advanced fluid dynamics based on a balance of inertial, viscous and capillary forces, it is possible to determine the impact velocity of the bloodstains. Accordingly, the curved trajectory can be calculated by taking gravity into account. Based on real bloodstain impact patterns we show that with our method the location and height of the origin can be determined much more accurate than the current methods in use.