Validating the morphology of 3D-printed cranial projectile trauma as a skeletal alternative for utilisation in a court of law

Abstract

Forensic anthropology has become crucial for global cases involving firearm-related injuries. Although skeletal evidence is valuable, its presentation in court may re-traumatise families or bias reactions, influencing the verdict. To mitigate these risks, the adoption of 3D printing technologies in court has increased, allowing the handling of human remains without the drawbacks of presenting biological evidence. This study aimed to validate 3D-printed skeletal technologies as alternatives for courtroom evidence, focusing on cranial bullet defects through 3D topographical analysis and investigating the accuracy of 3D-printed skeletal models. Samples were scanned using micro-focus X-ray computed tomography; their 3D meshes were generated, 3D printed using powder Selective Laser Sintering, resin Stereolithography, and polylactic acid (PLA) filament Fused Deposition Modelling technologies, and scanned again. The reference and 3D print meshes were aligned, and a colour map allowed visual inspection of morphological discrepancies of up to 1 mm (0 mm shown in blue, 1 mm in red). Powder-based prints exhibited the highest accuracy for representing crania, predominantly coloured dark blue (0 mm). PLA filament prints were accurate for examining smaller cranial surfaces (mostly 0 mm), whereas resin prints were the least accurate for crania (mostly 0.5-1 mm). 3D-printed skeletal material can be utilised in legal settings with a colour map elucidating discrepancies. While powder-based prints are preferred, other materials may better suit specific applications. Further research should evaluate the impact of 3D prints on judicial decision-making and refine 3D printing techniques for forensic anthropology.

HIGHLIGHTS • Skeletal evidence in court has psychological and practical limitations. • 3D-printed skeletal models’ morphological accuracy was investigated for court use. • Powder-based prints showed the highest accuracy for entire skulls and crania. • PLA filament prints are more accurate in cranial sections of entry bullet wounds. • The printer calibration and segmentation process impact morphological accuracy.