Research On The Added Printing Alteration

With the popularity of office automation, it has become a typical way to alter a document by added printing. The forensic document examiners have been asked to determined the documents alteration more frequently then before. Modern word processors enable one to edit a document and then print it so that the alteration cannot be easily detected on the document. Traditionally,the printing characteristics, e.g. printing manner, printer model and other detail features, have been regarded as the priority and essence of questioned printed document examination, while other high-reliable methods have been ignored. The current published researches mainly focused on a certain aspect or case report, while the systematic and comprehensive methods for identifying the added printing alteration are still missing. The author intended to make an empirical research, explore new ideas of examination, increase examination methods, and improve the detection of added printing alteration from the methodological point of view.The whole paper is composed of five chapters. The first chapter introduces the concept and features of added printing alteration, as well as a brief review of the present examination methods. Although the printing characteristics of documents printed by different types of printers look similar, there are differences in the printer’s configuration and the components of ink/toner. The author analyzed the components of various printed samples through experiments.The second chapter to the forth chapter describe the experiments including sample collection and data analysis of the common brand printers on the market. The second chapter presents the differences of the morphological feature between various brands and types of printers through the empirical research.The third chapter presents the difference in tracking code between several brands and types of color laser printers. The forensic document examiner needs to understand the positions and dot shape to distinguish the added printing alteration. The forth chapter is about component analysis.The printed samples were characterized and analyzed by infrared spectroscopy and in Via Raman microscope explore the possibility of identifying added alteration from the difference in the composition of print ink/toner.The applicability of chemometrics as a viable method in the discrimination of toners is explored. The printed text on paper can be distinguished by Raman. This method can also be applied in the examination of identifying seal inks, and provide a good supplement for the verification of the authenticity of questioned documents. The fifth chapter presents some typical cases which were examined from the aspects of layout,typesetting and printing to identify the.The research proves that those elements affects the examination on the added printing alteration. Different cases have different emphasis and a variety of examination methods should be carefully used to ensure the correctness of the conclusion. Variable methods can be used to detect the alteration of addition according to the different characteristics.