Doç. Dr. Ali Gelir, Istanbul Technical Universtiy, Physics Eng. Dept.

Prof. Dr. Faruk Aşıcıoğlu, Istanbul University-Cerrahpasa, Institute of Forensic Sciences

Ayşegül Şen Yılmaz, Istanbul University-Cerrahpasa, Institute of Forensic Sciences

It is very important to analyze the handwritings or marks on the documents correctly without damaging the sample in order to understand the forgery made in the document for forensic evaluations of the document. These analyzes can be exemplified as revealing the order of the intersecting lines, determining the letters and numbers that are added or deleted later, and identifying the grooves left by the pen on the paper.

SEM, optical profilometer, multi-wavelength optical systems, chemical, electrostatic and magnetic methods are currently used to perform these analyzes. Unfortunately, while some of these methods are very difficult and costly to implement, some of them can damage the sample. Therefore, there is still a need for new techniques for analysis which are low cost, do not damage the sample and easy to use.

In this study, the 3D scanner based techniques, which is easy to apply, can display line grooves successfully and is a low cost method, was used. Figure 1 shows a schematic drawing of the experimental setup. In this drawing, multiple photographs are taken from different positions and angles by rotating the sample on the turntable, and by combining these images, a 3-dimensional view of the surface is created.



Figure 1. A schematic drawing of experimental setup with a 3D scanner.

Figure 2 shows a sample scanning and the results of the analysis of the lines at the intersecting region. It is clearly seen in this figure that the 3D scanning method is capable of displaying the line grooves. It was observed that the depth profile along the line drawn first in the intersection area is different from the profile of the line drawn later as seen in Fig. 2 (d). This result clearly indicates that the 3D scanner can be used for the analysis of the handwritings in forensic evaluations.



Figure 2. 3D scan images of the intersecting lines (a and b) and the results of the analysis (c and d).