Hi Joe,
I remember someone asking Roy Castle (shortly before he died) what he thought of his imminent death. He replied "Well nobody's ever come back and complained!" Which is true as nobody does ever come back in body to tell us! What we have, when you watch clairvoyants such as John Edward or Colin Fry, is the deceased (if you can believe your ears!) coming back and communicating via a third person. As there is no face-to-face communication, the details of their readings can be either spot on or sketch y to say the least! Many people think such things are a load of rubbish and many people think they are true, which unfortunately does not answer your question!
If you saw a clairvoyant who told you things that nobody else but yourself knew to be true, then that would be your evidence but that does not mean that everyone else is going to believe you when you tell them, unless they experience it for themselves.