Abstract:
Toolmark identification is a well established discipline of forensic science. Qualified toolmark examiners are often confronted with the question of whether a suspect tool could have made a toolmark associated with a crime. Such an assessment is possible because certain manufacturing processes create unique marks on a tool's surface. Unique marks are also accumulated through damage, wear and corrosion. The pattern of unique marks present on a tool's surface can be transferred to an object. Toolmark identification involves determining if a toolmark and a tool share an overwhelming correspondence of unique marks. If so, it can be concluded that the toolmark was made using the tool.
Stabbing is one of the highest causes of homicide in New Zealand. Retrospective studies have shown that a bone is commonly marked during a lethal assault with a tool. This thesis aimed to determine if the techniques used in traditional toolmark identification could be applied to toolmarks in bone.
Three straight-edged boning knives, three serrated knives and three axes were used to make striated toolmarks in de-fleshed pig bone. The striated marks were cast with Mikrosil® and viewed using the comparison macroscope. The examination revealed that bone had the potential to record detailed striated marks. In some instances a striated toolmark in bone could be identified back to the tool that made it.
The axes were used to make chop marks in bone. Examination of the chop marks showed that enough detail was present in the marks for an identification. However, a comparison of the same chop mark cast at different time periods revealed that the chop marks in bone were changing. This meant that although there was detail present in the chop marks, an identification could not always be made because of discrepancies in the position and size of the characteristics.
The results of the study have shown that bone has the potential to record microscopic detail. In some instances it can be concluded that a specific tool made a particular toolmark in bone. However, being a preliminary study, this project has identified other factors that should be addressed regarding the evidential value of toolmarks in bone.