Potential explanations for noises on telephone lines
The IOPC sought to examine potential explanations for the noises that people heard on their telephone lines, other than that they were a result of police surveillance. Investigators contacted three telephone engineers who had experience of supporting official surveillance during the 1990s and 2000s. They all indicated that if there had been authorised surveillance of telephone lines, the users would not have heard anything. This was because of the way such surveillance was conducted. They also suggested that in this period, crossed lines—that is, hearing a different conversation—sometimes occurred as a result of either a fault or water ingress on the line.
The IOPC also appointed an expert witness on surveillance, who had been part of the surveillance team at the Metropolitan Police Flying Squad. He was asked to comment on various matters, including the noises that complainants had heard on their telephone lines. He said that, as far as he was aware, authorised interception of communications took place in a sterile environment where “it would be impossible to hear intruding voices.” He also observed that if voices could be overheard during an interception operation, it “would completely jeopardise and compromise the process.” He could not offer an explanation for the clicking noises heard.
Together, these responses indicated that the noises were unlikely to be a result of official police surveillance.
