The present document describes the data content of a Lawful Interception interface in a TETRA system. It provides the requirements and specification of the interface within a TETRA system for the purpose of providing data to Law Enforcement Agencies (LEAs) in the area of Lawful Interception (LI) of communications.The present document describes the internal LI interface of a TETRA network, and does not specify the means by which data is delivered to the LEA or to its designated Law Enforcement Monitoring Facility (LEMF). However the internal LI interface is defined in such a way that data may be carried transparently on most networks.