Abstract:
Blood spatter resulting from a cranial gunshot wound travels in two directions; some blood exits through the bullet exit wound, and some blood travels against the line of fire through the entrance wound. This blood is called back spatter and actually comprises bone fragments, blood, skin and brain tissue. Back spatter can be found on the hands of the shooter as well as on the firearm used. It can therefore, be useful in differentiating between suicide and homicide. However, back spatter is not always produced from cranial gunshot wounds and the situations that lead to its production are not understood. To date, no model has been able to accurately depict the back spatter phenomenon. Modelling cranial blood spatter requires investigation into bone, blood, skin and brain tissue simulants. In this thesis, the behaviour of brain upon bullet impact was investigated with the intention of incorporating a brain simulant into a back spatter model. The uniform and homogeneous nature of ballistic gelatine has made it a popularly used muscle simulant. 10 % ballistic gelatine has been validated as a muscle tissue and has also been used as a brain simulant. 10 %, 5 %, 4 %, 3 % and 2 % ballistic gelatine was compared to bovine brain tissue by way of energy absorption. 1.5 % and 2 % agar as well as 0.5 % agarose was also compared to bovine brain tissue. The different concentrations of gelatine, agar, agarose and brain tissue were fired with 9 mm projectiles, the projectiles’ velocities and depths of penetration were then recorded. The relationships between projectile velocities and depths of penetration in the simulants were compared to this relationship in bovine brain tissue. The energy transfer of a 6 mm projectile travelling at approximately 300 m/s through bovine brain tissue, 2 %, 3 %, 5 % and 10 % gelatine was also investigated. The 3 % gelatine and 1.5 % agar were found to be the most similar to bovine brain tissue in terms of energy absorption.
