This European Standard (Telecommunications series) provides the requirements and stage 1 implementation for Terrestrial Trunked Radio (TETRA) systems in the area of Lawful Interception (LI) of communications. It provides a set of requirements relating to LI interfaces for use by Law Enforcement Agencies (LEAs) and state security agencies. This present document is structured as follows: - clause 4 outlines the essential requirements of the LEAs; - clause 5 is an ITU Recommendation I.130 [3] (see annex B) type stage 1 technical description of the LI interface; - annex A contains explanatory diagrams to assist the reader to understand the requirements; - annex B summarizes the methods of ITU Recommendations I.130 [3] and I.210 [4]; - annex C contains a bibliography. Pending national legislation not all requirements may be applicable in one individual nation. The present document applies to TETRA services where access to the communication of Individual TETRA Subscriber Identities (ITSIs) is available in a network (Switching and Management Infrastructure (SwMI) or Radio Packet Data Infrastructure (RPDI)). Whilst this does not prohibit lawful interception of TETRA Direct Mode Operation (DMO) it removes the liability of network operators and service providers to provide an interception product when communication does not make use of their networks. The present document does not define the operations or technical requirements of the Law Enforcement Monitoring Facility (LEMF).