Examination of digitally captured signatures for questioned document

In Forensic Document examination, which is a very broad field in the forensic sciences, the most common types of cases include examining the questioned documents that have caused legal disputes, usually prepared on paper, and determining the identity of the signature on them. With developing technology, transactions in many sectors are now carried out in digital environments in order to reduce paper usage and increase the reliability od documents and elevate speed of transaction processes. Especially with the development of public key infrastructures that secure documents with asymmetric encryption, the use of electronic signatures has become widespread, and digitally captured signatures, which function similarly to electronic signatures, have begun to be actively used in the flow of business life. In parallelly the crimes committed on documents have changed according to technological developmets, and documents prepared electronically and signed digitally have begun to cause legal disputes. In this situation, which judicial authorities have just encountered within the scope of electronic document forgery, the lack of laboratories with the appropriate infrastructure and lack of experts to examine digitally captured documents or signatures poses a problem. The main reasons for this are the fact that different hardware and software are used in obtaining and examining signatures in this process, which is new all over the world, and that the international standards to be used in signatures have just begun to be established. In the first part of the study, it is aimed to examine whether the digitally captured signatures of individuals show variation over the one year period of time. In the second part, in case digitally captured signatures are imitated, it is aimed to compare the data of the forged signatures with the data of the original ones and to detect the data that separates them. Thus, it is aimed to obtain information, which are not yet included in the literature, about how the digitally captured signature data of individuals has changed over time, and to contribute to forgery studies by examining signatures with different types of complexity. In the last part of the study, it is objected to normalize the force by determining the correlation function between the pressure of the capacitive screen tablet and applied force. In the literature, no study has yet been conducted with the brand and model of capacitive tablet and its compatible passive capacitive pen used in this study, and there is no information about the correlation of pressure value of this tablet and applied force via its stylus pen. This study aims to fill the gap in the literature.