Yet another Labour technological failure
There are simply too many signal degradations over any telephone carrier system to make these detectors accurate.
Whether 'landline' or cell all systems introduce phase distortion, flutter, audio frequency changes, etc. which are readily recognisable by telephone users.
Many countries have tossed out lie detector equipment, except for the U.S.A., as most courts recognise they are not accurate and their output requires 'interpretation' which can introduce bias.
These voice stress systems use similar principles. A pathological liar will always show 'true' readings as they believe their lies.