Obviously, the very best way to catch someone in a lie is to be in the room with the facts while they are speaking.  The next best thing is voice activated recorders.  They will give you the same results as being in the room when a conversation or a phone call takes place.  You do not have to let the recorder run, wasting tape or disk space and time.  The recorder will begin operating the moment someone speaks.  The machine will pick up every word and then when the speaking is finished it will shut itself off.  You will finally have what you need.