Use of data in criminal procedure which are obtained for preventive purpose

In this study, usability of data in criminal procedure which are obtained by preventive or intelligence activities is being examined. There are many different methods resulting in obtaining data for preventive purposes. In the study, in addition to methods such as MOBESE (CCTV), preventive search, interception of telecommunication, control of internet traffic data; trawl method, fingerprint database, X informant's statements are also discussed. Besides, some foreign law regulations; co-operations based on international data sharing, EU directives and also ECtHR's approach to the subject are examined within the scope of this study. General purpose of these activities is prevention of crimes; therefore usability of such data for judicial purposes is controversial. In accordance with principle of compatibility with purpose, the main rule regarding this issue is; usage of the data compatible with obtaining purposes. Thus, the fact that a data has been obtained by official authorities, does not mean that it can be used for any purpose without restrictions. Unlimited use of data obtained by preventive or intelligence activities by judicial authorities may lead to different authorities undertaking the task of judicial authorities and loss of judicial forces' functions and criminal procedural safeguards. On the other hand, in the case of judicial authorities' total disregard of these data may cause impunity. In addition, the issue should be discussed in the aspect of totalitarian state formation. Keywords: Preventive Measures, Personal Data, Data Processing, Intelligence, Interception of Telecommunication, Legal Evidence.