The development of technology has challenged legislation in several areas during the last decade. The increase in the amount of data and computer performance, and new software solutions such as artificial intelligence and computer linguistics based intelligent search require a reassessment of the legal barriers to their operations. On the one hand, law enforcement agencies and security services demand increasing access to these technologies to come up to the social expectations in the field of security. On the other hand, civil rights organizations require an ever-stronger oversight of law enforcement agencies and security services to avoid their possible abuse of the most advanced technologies. The paper argues that the only way to resolve this dilemma is to improve the accountability of law enforcement agencies and national security services, thereby increasing public trust. Procedural and technical methods to perform this task are examined. The corresponding EU legal framework is analyzed.