To that end you can visit David at one of the Spiritualist Churches or have a private consultation and see a demonstration of medium-ship.
The main purpose of this demonstration is to provide that evidence, to give proof of survival, not to predict the future, not to give advice and certainly not to counsel.
Every Spirit medium that takes to the public platform or stage needs to know what constitutes proof of survival. In many respects this will be personal to the recipient of the message, so, if you are the recipient, or the giver of a message, ask yourself the Following questions:
Was identity established?
How did you know who was communicating? 
Did Spirit convey knowledge of recent events?
Was there a pertinent message?
Look for an appropriate combination of the following facts which identifies one communicator beyond reasonable doubt:
Name Address (this does not mean postal address and post code, but any information about where they lived)
Relationship
Age
Description
Profession
Method of conditions of Passing, (only if necessary)
Character Shared memories
Together with a pertinent message or proof of on-going intelligence.
Proof of On-going Intelligence
This is important because it is evidence that supports the fourth principle, `The Continuous Existence of the Human Soul`.
If we only received information about a person or events prior to their passing it would not do this. We often get messages from Spirit telling us about events in our everyday lives, like- "I saw you in your kitchen yesterday, and you dropped a glass", you may think a message like this is quite unimportant and may seem trivial. However, it`s importance must not be overlooked, because through Knowledge of recent events it shows us that the person lives on.
If we only received information of events that happened prior to the communicating passing, it would not prove life after death, so we must look for new information that they have added to their memory.
Why one communication?
A common failing in medium-ship is to give a little information about a lot of people;
lists of names are not evidence. Remember you are communicating with a person; it is a two way communication. Ask them for more information before you move on to another communicator.
It is more important to establish, beyond reasonable doubt, the identify of a single person, than to reel off lists of names or brief descriptions like:
"I have a man with grey hair"
That proves nothing.
David builds up a picture of the person he is communicating with in his minds eye of the recipient. Leave them knowing, not just thinking they know, who you have. By bringing through the personality and character, along with pertinent facts you will be providing the evidence that so many are looking for, and thereby
David feels contented knowing he has provided you with a message based on truth and integrity. He is blessed with a remarkable gift from the spirit world and uses his sixth sense to help those people who seek re-assurance of eternal life.
Spirit operators and David have an agreement they work with honesty and professionally at all times and bring comfort to the bereaved.
Happiness is only a smile away (Spirit quote)