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

With the recent surge of commercially available 3D printing technologies, untraceable firearm components are being created with ease. As these firearms become more popular, there is a need for viable methods of source identification for these 3D printed objects. Both the printer hot end nozzles and print bed surfaces leave distinct characteristics that are observable upon surfaces of the 3D printed objects. Few studies focus on toolmark analysis of 3D printed evidence, and fewer utilize algorithms to determine the similarity of these toolmarks. The goal of this research was to determine if toolmarks found on 3D printed objects are distinct and reliable enough to be used for source conclusions. To test this, 150 printed objects were created with 10 different print beds and 10 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, giving each comparison a score between 0.0 and 1.0 depending on the similarity of the surfaces. All print bed surface and nozzle surface scans were intercompared, resulting in 11,175 comparisons for each top and bottom surface. Data were analyzed using receiver operating characteristic (ROC) curves and area under curve (AUC) scores. AUC scores demonstrated that the algorithm was able to consistently 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.