a method of conducting covert surveillance of a subject is provided for within a telecommunications network . the surveillance includes surveillance of a monitored call connected over the network , the monitored call being between the subject and an associate and including circuit - switched or packet - switched call content , i . e ., bearer traffic exchanged between the subject and the associate . the method includes : clandestinely receiving the circuit - switched or packet - switched call content ; converting the received circuit - switched call content into a packet - switched format ; and , delivering the call content in the packet - switched format to a designated law enforcement agency over a packet - switched data network .