OSCILLATING BLOOD DROPLETS - IMPLICATIONS FOR CRIME SCENE RECONSTRUCTION

Traditionally, the analysis of blood spatter on surfaces in the recons truction of crime scenes relies on the assumption that blood droplets are spherical when they strike the surface. This paper explores the ef fects of their shape on the reconstruction of trajectories from their impact pattern, and reports a theoretical analysis of the lifetime of droplet oscillations. Oscillations damp quickly in blood droplets due to the viscosity. The analysis provides ranges of velocities and dista nces from the point of droplet projection within which it is unreliabl e to assume the droplets are spherical when they stain a surface. Non- spherical droplet stains predict incorrect positioning of the droplet projection point. Experimental data are presented to show that the est imates apply in practice.