The Hidden Truth (1967-1969) Episodes of this radio program opened with "The truth, the whole truth, nothing but the truth, the hidden truth". This South African program was based on the real-life cases of criminologist Leonard Keeler, co-inventor of the polygraph, or lie detector, machine. Hart Maguire played the part of Keeler, a man who could, literally, smell a lie. Refusing to be baffled by crime, he always finds what he is after: The Hidden Truth.