The social nature of human beings pushes them for social interaction and each human being has their own interests, which may not always coincide with the interests of other individuals. Therefore, a state’s high priority task is to ensure that every human being and the whole society is protected by the state from unlawful acts. The state is obliged to take legal means to disclose the criminal acts committed by the individuals, and limitation of human rights and fundamental freedoms is inevitable. It means that law enforcement agencies can enter a person’s private life protected by international and national law. In given situations, a form of competition arises between the two legal values protected by the law: the right of the people to be secure in their persons and the right of person to privacy and dilemma how to tackle in case of collision of two mentioned values during pre-trial investigation. Based on international standards formulated by European Court of Human Rights, a person’s right to privacy can be limited in some cases if such restrictions procedures, in details, are prescribed by law. Mandatory requirements for law restricting a person’s privacy are: accessibility (publicly accessible for everyone who wish to introduce); targeting legal objectives; possibility to protect a person‘s rights from illegal actions; foreseeability; necessity in the democratic society for the prevention of disorder or crime; state‘s interference into a person‘s privacy must fit pressing social need. The states (signatories of 1950 European Convention on Human Rights) enjoy a certain but not unlimited margin of appreciation in the matter of the imposition of restrictions on a person‘s right to privacy. [...]

The restoration of the independence of the Republic of Lithuania on 11 March 1990 ipso facto implies the beginning of buildup of the new legal system in Lithuania and succession of the best Western values legal traditions. At the same time it is considered to be the starting point for the legal system of the Republic of Lithuania from which it has been beginning to evolve and develop into the direction of respect for human rights and fundamental freedoms. This is clearly reflected in the Constitution of the Republic of Lithuania adopted by citizens of the Republic of Lithuania in the Referendum of 25 October 1992. The preamble of the Constitution of the Republic of Lithuania provides that one of the most significant aims of the Lithuanian nation is to strive for an open and harmonious civil society and law-based state. The social nature of human beings pushes them for social interaction and each human being has his own interests which may not always coincide with interest of other individuals. Therefore, a state’s high priority task is to ensure that every human being and the whole society is protected by state from unlawful acts. The state is forced to take legal means to disclose the criminal acts committed by the individuals, and limitation of human rights and fundamental freedoms is inevitable. For this purpose, legislation has granted law enforcement authorities the right to use special investigative techniques in conducting the prosecution. It should be noted that the special investigation techniques such as controlled delivery, covert surveillance, electronic surveillance of all forms are legitimate and internationally recognized e.g., 1988 The United Nations Convention against Illicit Traffic In Narcotic Drugs and Psychotropic Substances. That encourage national lawmakers transform special investigation methods from criminal surveillance law to criminal procedure law.