Three-dimensional detection of sequence of strokes using confocal microscope

Abstract

Background: In the present study, three-dimensional application of confocal microscope is explored. The aim is to determine the sequence of intersecting lines written on a questioned document as a non-destructive technique. The authors have tested the Nikon confocal A1 microscope on two major criteria. The criterion 1 focuses on the analysis of homogenous intersecting lines, whereas the criterion 2 focuses on the effect of pen pressure on the sequence of the strokes. Fifty-four and 42 samples from criterion 1 and criterion 2 respectively were examined. All the intersecting strokes were homogeneous and in either black- or blue-coloured ink. They were made from glycol-based (ballpoint pen) and liquid-based (fountain pen and gel pen) inks. Result: The authors were able to determine the correct sequence of homogeneous intersecting lines in 81 and 83% of the average data of samples for criterion 1 (the analysis of homogenous intersecting lines) and criterion 2 (the effect of pen pressure on the sequence of the strokes) respectively. Conclusion: The confocal microscope proved to be a reliable and precise technique for analysing the homogeneous intersected lines made by any pen pressure beyond all the errors during interpretation.