Abstract:
The aim of this thesis is to determine the uncertainty associated with the use of the Faro Focus 3D S 120 laser scanner in determining bullet trajectories at crime scenes and, in doing so, to produce a method of best practice for laser data capture and processing of crime scenes where shots have been fired. A bullet trajectory is recorded by laser scanning target spheres on a trajectory rod that is placed through a bullet hole. The trajectory is realised and displayed using specialist software. Each step in this method was analysed and the determined uncertainty found was minimised where possible. The highest source of uncertainty was determined to be associated with the trajectory spheres used to mark the path of a bullet as it entered a surface, as the centre point of the spheres varied depending on the surface scanned. The uncertainty of the best practice method was determined for three different trajectory sphere types. The maximum observed angle of uncertainty and maximum expected angle of uncertainty, respectively, for each sphere type were 0.718° and ±1.358° for table tennis balls; 0.687° and ±1.336° for polystyrene spheres and 0.608° and ±1.092° for 3D-printed spheres. The Faro Focus 3D laser scanner was found to determine the trajectory to a suitable angle of uncertainty for all three sphere types, based on the accepted uncertainty of manual determinations of ±5°. Further research is required into spheres with a more accurate central trajectory rod hole to advance this method.