Scanning White Light Interferometry, — A new 3D forensics tool

Three dimensional (3D) imaging has been introduced into forensic work. Quantitative height data adds information compared to the conventional 2D-images when micro-scale evidence is studied. We show the potential of Scanning White Light Interferometry (SWLI) as a 3D imaging method for forensic studies. SWLI allows rapid, non contact measurements of millimeter-size objects with nanometer vertical resolution without sample preparation. We compared toolmarks and to examined crossing lines on metal. When studying marks made by diagonal cutters on wires and firing pin impressions on cartridges we could match cases that were hard to match with a normal forensic microscope. When studying crossing lines the confidence of the examiner was improved from 3.3 ± 1.9 / 5 to 4.2 ± 0.9 / 5 when using 3D images.