Determination of crossing sequences between seal impression and laser-printed lines based on characteristics of the toner molten state.

Abstract

Determining the sequence of intersection lines is a challenge in forensic document examination. To explore more advanced technology and meet the needs of practical applications, this study proposes a method based on the characteristics of the molten state to examine crossing-line sequences. This state can be considered as a melting state of solid laser toner through a dissolution process. Experimental results demonstrate that the molten state is always visible at intersections when a particular ink is stamped after laser printing; however, the presence of the molten state when the seal is stamped before laser printing largely depends on the time interval between printing and stamping. The degree of error obtained through blind tests indicates that this approach has its limitations; however, a high accuracy, which refers to the ability of an examiner, was achieved with respect to determining the sequence of strokes when using a fluorescence method in conjunction with this method. This further indicated the limitation of a single method and the importance of combining multiple methods for document examinations.