3D printed object topography analysis and the viability for forensic examination

Abstract

With the recent surge of advanced commercially available 3D printing technologies, individuals have the ability to create virtually untraceable firearm components from the comfort of their home. As these untraceable firearms are becoming more popular, there is a need to determine viable methods of source identification of these 3D printed objects. Both the printer hot end nozzle and print bed surfaces leave distinct characteristics that are observable upon the surfaces of the 3D printed objects. It is hypothesized that the thermoplasticity of the polymers used for printing inherits the characteristics present on the print bed surface and microscopic characteristics of the hot end nozzles used to print the objects. There have been few studies on the topic of the forensic analysis of 3D printer related evidence, and fewer that use advanced algorithms to objectively determine the similarity of 3D printed evidence. The goal of this research was to determine whether toolmarks found on 3D printed objects are distinct enough to identify or exclude a 3D printed object as originating from a specific source. To test this, 150 printed objects were created with ten different print beds and ten different nozzles, with 15 prints for each bed-nozzle pair. 3D scans of the top and bottom surfaces of each object were made using the Cadre Forensics TopMatch-GS system. Cadre’s pattern-matching algorithms were then applied to the 3D scans, which gave each comparison a score between 0 and 1.0 depending on how similar the surfaces are. All bottom and top layer scans were intercompared, resulting in a total of 11,175 comparisons for each top and bottom surface. The data was analyzed using receiver operating characteristic (ROC) curves and area under curve (AUC) scores. AUC scores demonstrated that the algorithm was able to consistently and correctly differentiate between same and different source printed objects. This study demonstrates that source identification of 3D printed objects using toolmarks may be viable for forensic examination.