Elliptical Fourier analysis of bullet ricochet impact site plan-view shape in concrete

Bullet ricochets often leave impact sites that can be useful for shooting incident reconstruction. Here, we assess the proposal that these sites can potentially provide information about the design and composition of the projectile and possibly the corresponding firearm. We produced impact sites in concrete from five bullet types fired at two distances, for a total of 10 experimental conditions. Then, using elliptical Fourier analysis, we assessed the 297 bullet ricochet impact sites' plan-view outline shapes. Of the different bullet types, the 45 calibre Hollow Points exhibited the greatest variability in ricochet impact site shape, and the greatest potential for diagnosis. Overall, statistical assessment of robust sample sizes of ricochet impact sites suggests that there is too much overlap between different bullets' ricochet sites' plan-view form for confident identification of bullet design and composition, much less identification of the firearm from which it originated. We conclude with an extended discussion about future experiments involving bullet ricochet impact sites, including the employment of "paradigmatic classification", which can both organise the testing of experimental variables as well as illustrate the tremendous amount of experimental work that still needs to be conducted before researchers or firearm examiners draw firm conclusions. Key PointsBullet ricochet impact sites often occur in shooting incidents.We analysed bullet richochet impact site shapes in concrete using elliptical Fourier analysis.Results suggest different bullet types' ricochet impact shape morphospaces overlap with each other.This overlap obscures conclusions about the design and composition of the projectile and possibly the responsible firearm.