Evaluating Simulant Materials for Understanding Cranial Backspatter from a Ballistic Projectile

Abstract

In cranial wounds resulting from a gunshot, the study of backspatter patterns can provide information about the actual incidents by linking material to surrounding objects. This study investigates the physics of backspatter from a high-speed projectile impact and evaluates a range of simulant materials using impact tests. Next, we evaluate a mesh-free method called smoothed particle hydrodynamics (SPH) to model the splashing mechanism during backspatter. The study has shown that a projectile impact causes fragmentation at the impact site, while transferring momentum to fragmented particles. The particles travel along the path of least resistance, leading to partial material movement in the reverse direction of the projectile motion causing backspatter. Medium-density fiberboard is a better simulant for a human skull than polycarbonate, and lorica leather is a better simulant for a human skin than natural rubber. SPH is an effective numerical method for modeling the high-speed impact fracture and fragmentations.

Geometric and mechanical evaluation of 3D-printing materials for skull base anatomical education and endoscopic surgery simulation – A first step to create reliable customized simulators

“…Das et al [ 29 ] also used PC to simulate skull bone for ballistic projectile evaluation. They consider PC to be too ductile for this application, which confirms the need to carry out mechanical tests specific to the chosen application.…”

Ten years of molecular ballistics—a review and a field guide

“…Easy handling due to spheric form, difficult to replicate Polyethylene Grabmüller et al [ 20 , 21 ], Schyma et al [ 51 ] Polyethylene bottles, easy to obtain and handle, stable, but different mechanical properties Skin Chamois leather Euteneuer et al [ 81 ] Used and recommended by the German Federal Criminal Police Office Semi-finished chrome tanned upholstery “crust” cowhide Jusilla et al [ 82 ] Best skin simulant in a comparison study with 13 materials. Still partly natural product and thus prone to variation Silicon with artificial fibers Thali et al [ 71 ] Results comparable to real cases Dental silicon Falland-Cheung et al [ 83 ] Suitable material with mechanical properties comparable to fresh porcine skin Lorica leather Das et al [ 84 ] Better skin simulant for backspatter compared to natural rubber, at shots with 9 mm Luger Roebuck 1518 synthetic chamois Pullen et al [ 85 ] Suitable skin simulant for tests with non-deforming bullets. Silicon Misc.…”

“…The skin simulant used in the “skin-skull-brain” model by Thali et al consists of silicon with artificial fibers and produced results comparable to real cases [ 71 ], while Felland-Cheung et al described dental silicon as an alternative for skin in a study comparing dental materials as simulants to fresh porcine skin [ 83 ]. Das et al evaluated simulant materials for cranial backspatter and while only employing very limited materials, they concluded that lorica leather is a better skin simulant than natural rubber for backspatter testing [ 84 ]. In a recent study, Pullen et al evaluated Roebuck 1518 synthetic chamois (RBK) backed by 10% gelatin for ballistic and forensic use and confirmed this material’s suitability as skin simulant with test using non-deforming projectiles [ 85 ].…”

Cranial Backspatter Pattern Production Utilizing Human Cadavers

“…The presence of backspatter on the hands, arms, and clothing of suspects and victims, as well as on the firearm, has been used in reconstructing specific aspects of bloodshed in firearm‐related injuries . The use of animals such as cows , pigs , and sheep , as well as objects like blood‐soaked sponges , skull simulants , resin calvaria , and blood‐filled coconuts , has been used to demonstrate the characteristics of backspatter stains and how the patterns are created. The use of live animals is generally not feasible when training new analysts on observing the characteristics of a backspatter pattern or for some controlled studies.…”