A novel method for linking between a 3D printer and printed objects using toolmark comparison techniques

The use of micro-CT in the investigation of a case involving 3D printed firearms

This paper highlights how micro-CT was used to assist in the investigation of hybrid firearms constructed using a mixture of plastic and metal components, as a complementary technique to the physical examination performed by firearms experts. In recent years, there has been an increase in the complexity and sophistication of 3D printed and hybrid firearm designs. This was also the case in the investigation presented herein, with the firearms seized demonstrating a step change in the threat level they pose through their complexity. Thus, we describe how data produced from micro-CT scans was used to help firearms experts study the viability and mechanics of two hybrid weapons prior to dismantling and test-firing. This process aided experts in determining whether components were 3D printed or manufactured through other means, whilst ensuring that a digital record (digital twin) was retained in case evidence was damaged during testing. Finally, we show how the data was presented visually through animations and as evidence in court. This proved to be imperative when communicating to the judge, jury, and wider investigating teams, the complex multiple components and mechanisms within the firearms.

Improving Estimation of Layer Thickness and Identification of Slicer for 3D Printing Forensics

This study emphasizes the significance of estimating the layer thickness and identifying slicer programs in the realm of 3D printing forensics. With the progress in 3D printing technology, precise estimation of the layer thickness has become crucial. However, previous research on layer thickness estimation has mainly treated the problem as a classification task, which is inadequate for continuous layer thickness parameters. Furthermore, previous studies have concentrated on hardware-based printer identification, but the identification of slicer programs through 3D objects is a vital aspect of the software domain and can provide valuable clues for 3D printing forensics. In this study, a regression-based approach utilizing a vision transformer model was proposed. Experiments conducted on the SI3DP++ dataset demonstrated that the proposed model could handle a broad range of data and outperform the current classification models. Additionally, this study proposed a new research direction by introducing slicer program identification, which significantly contributes to the field of 3D printing forensics.

An exploratory study of topographical signatures within 3D fused deposition modelling using Polylactic Acid (PLA) filament

This preliminary limited study considers the possibility of the same source identification of consecutively 3D printed components using polymer filament by the examination of deposition artifacts as distinctive macroscopic and microscopic surface characteristics upon the surface of 3D printed objects. Hot-end printer nozzle deposition using polymer filaments can create distinctive surface characteristics upon 3D FDM-printed manufactured objects that can be identified, examined, and compared. Such artifacts can occur as repeatable patterns known as 'deposition striae', 'detachment points', and 'start points' upon the surfaces of an object and on consecutively manufactured components that have used the same 3D Fused Deposition Modelling (FDM) printer hardware. Some of these observable artifacts can fulfil the sufficient agreement requirements of the Association of Firearm and Tool Mark Examiners (AFTE) Theory of Identification as it relates to tool marks when applied to consecutively produced 3D Additive Manufacture (AM) components. For this criteria to apply, the influence of subclass characteristics on any identification must be ruled out.

Interpol Review Paper of Marks and Impression Evidence 2019-2022

This section contains an overview of publications relevant to advances in scientific methods and general discussions concerning shoe and toolmark examiners, which were published between January 2019 and May of 2022 and is the sequel to the review for the 19th Interpol International Forensic Science Managers Symposium in 2019 by Martin Baiker-Sorensen. A literature search was conducted covering relevant articles published in the main forensic journals.

Nondestructive Forensic Comparison of Nylon Trace Evidence Using Room-Temperature Fluorescence Spectroscopy

The increasing accessibility of 3D printers makes their use for criminal activity more likely. Current forensic analysis of trace evidence left by 3D-printed materials focuses on identifying the general type of plastic, which includes acrylonitrile butadiene styrene, polylactic acid, nylon, polycarbonate, polyethylene terephthalate, and chlorinated polyethylene. Herein, we present a nondestructive approach capable of differentiating among different types of nylons. The new approach is based on room-temperature fluorescence spectroscopy. Excitation-emission matrices, excitation and emission spectra, and synchronous fluorescence spectra are directly recorded from single microplastics with the aid of a fiber-optic probe coupled to a commercial spectrofluorometer. The comparison of spectral features demonstrates the capability to differentiate microparticles originating from Nylon 11, Nylon 12, Nylon 6/6, and Nylon 6/12. The observed differences are attributed to the presence of fluorescent impurities embedded in the polymer during its fabrication. The outstanding matching of excitation-emission matrices, excitation and emission spectra, and synchronous fluorescence spectra demonstrates the potential of this approach to link trace evidence to a specific source beyond its general plastic type.