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

Rapid advances and decreased production costs in 3D printing (3DP) have resulted in its accelerated implementation in criminal activities. Fused Deposition Modeling (FDM (3DP and Polylactic Acid (PLA) filament were chosen for the current research because they are widely used in commodity 3DP, particularly in documented criminal activities. This study shows how specific features of 3DP along with classical toolmark comparison techniques using Stereo-Microscopy and Comparison Microscopy can be used to link between two 3DP objects as well as between a printed object and a suspected 3D printer. Links are determined based on random fine marks found on the 3DP's heated stage (bed) that are replicated to the base face of the printed object. Melted filament that extrudes from the nozzle of the FDM 3DP constructs the base face of the printed object. This melted filament functions as a "casting material" after it cools down and solidifies, enabling replication of the fine marks. The observed resolution of these marks is as high as the resolution of casting material dedicated for toolmark replications. Overall, this study demonstrates a novel forensic method based on toolmark comparison for linking between a 3D printer and its printed objects.

A new method for opening quartz halogen light bulbs in vehicle accident investigations.

After a car accident, it is an important forensic task to evaluate the status of the vehicle's lighting at the time of impact. In some cases, the bulb has to be opened up to allow proper examination of the high and low beam filaments. Quartz halogen pressurized bulbs are both rigid and brittle and their internal pressure makes them likelier to explode. This study aimed to develop a more elegant method of breaking halogen bulbs open that would minimize the danger of explosion and the risk of damaging the filaments in the process. As part of the study, several opening methods were tried on multiple pressurized quartz halogen bulbs, such as cutting a groove with a hacksaw or a rotary tool, using a propane torch on the bulb to cut or warm it and then cooling it rapidly. Repeated testing by several examiners has shown that the new method developed in this study is the safest and easiest compared with other established methods.

Toolmarks made by lathe chuck jaws.

This paper presents a forensic method to evidentially tie a workpiece with a specific lathe. Examining using this method can prove or exclude a connection between the two. The importance of this method is mostly due to the growing trend among lawbreakers of manufacturing improvised firearm parts using machining processes. This method is based on comparing jaw impressions made by the chuck on a workpiece.