The study found that most impacts produced "internal wounds" or subsurface cavitation (96 percent). There were four internal "wound" types: Y-shape (53 percent); linear (25 percent); stellate (16 percent); and double crescent (6 percent). External wounds occurred for less than half of the impact; however, nearly all of the impacts resulted in internal wound. This might explain the haematoma formation and contusion often associated with blunt-force injuries. The study also confirmed the key role of hydrodynamic pressure changes in the tearing of subcutaneous tissue. At the moment and site of impact transferred kinetic energy creates a region of high pressure on the fluid inside the tissue. As a result of the incompressibility of the fluid, this will be displaced away from the impact at a rate that depends on the velocity (or kinetic energy) of impact and the permeability and stiffness of the polymeric foam and skin layer. In order to simulate skin and the sub dermal tissues, the study used open celled polyurethane sponge (foam) covered by a silicone layer. A drop tube device with three tube lengths (300, 400, and 500 mm), each secured to a weighted steel scaffold, provided channels to guide the descent of a 5-kg Federal dumbbell 180mm long and 8cm in diameter, which delivered blows of known impact. In order to calculate energy and velocity at impact, the experimental set-up was replicated using rigid-body dynamics and motion simulation software. Each foam square was soaked in 500 ml of water until fully saturated before placing it beneath the drop tube. Researchers then recorded and classified both external and internal lacerations. 3 tables, 5 figures, and 26 references