In order for the data that results from the technical surveillance to form a veritablemeans of proof, it is mandatory that such informations are not to be altered in any way and that theoriginal support in which the data was printed to be kept secure. In the context of a society in whichtechnological advancements are increasing at a rapid rate, there exists a real risk of altering suchevidence. As such, it is in the prosecution's duty to secure the data resulting from technical surveillance. If there is doubt regarding the authenticity of such recordings, the only method toverify the reality of the data resulting from technical surveillances is a criminal expertise.Such an expertise can be performed in the course of a judicial inquiry so that the court canverify if the technical surveillance data has not been altered or manipulated in such a way that theactions of the defendants may gain criminal connotations.The jurisprudence is not unanimous in this regard, but if an opposite hypothesis is to beacknowledged, it would lead to absurd situations. Rejecting an expertise proposed in order todemonstrate the authenticity or the forgery of the data obtained through technical surveillancemeans convicting a person on the basis of unverified proof, while the European Court claims anexpress a posteriori verification regarding all evidence materials.