CSI Helsinki: comparing three-dimensional imaging of diagonal cutter toolmarks using confocal microscopy and SWLI

Cutting tools leave characteristic marks that can connect a set of toolmarks to an individual tool. When the depth resolution of an optical microscope is insufficient, more advanced three-dimensional (3D) imaging methods such as Scanning White Light Interferometry (SWLI) and confocal microscopy are required. We cut ten copper wires (2.1±0.1 mm diameter) maintaining a predefined blade orientation and position using diagonal cutting pliers. Images of the sample surfaces were created using equipment based on optical microscopy, SWLI and confocal microscopy. SWLI and confocal microscopy set-ups can produce consistent high-resolution 3D images that are relevant for forensic toolmark comparison.