No need to apologise mate, it can get quite complex and confusing.
I'm basing what I know on experience as a former union rep and corporate trainer which included training managers on company disciplinary procedures and processes.
They have to notify you what they are charging you with and they would need to be specific so that you can prepare a defence (preparation).
For example, they couldn't accuse you of robbery and then spring a charge of assault at the hearing with evidence relating to this.
With regard to evidence, they can produce this at the hearing (presentation stage) just as we could do likewise providing it is relevant to the charge they have alleged during the notification stage.
This works both ways as I suspect they don't know what our "irrefutable evidence" is and we have every right not to divulge this to our accusers until the hearing just as they have every right not to divulge anything they have or think they have.
It would be up to the judge or judges (in this case arbitration panel) to look at the evidence presented from both sides and draw a conclusion. In this case, the panel would be akin to a jury in a standard court case.
If the case is on the basis of Civil Law (which I believe this is) then the judgement is based on the "balance of probability", in other words they must reach an outcome or conclusion based on what a reasonable person would think most likely happened.
In Criminal Law the judgement is "beyond reasonable doubt" and the accuser has to prove their case using a higher threshold in other words, the burden of proof lies with the accuser to prove their allegation rather than what likely happened.
The best example I can think of is to explain is OJ Simpson who was found not guilty in a criminal trial but found guilty in a civil trial after the family of the victims pursued this.
Every process has to have some kind of appeals process at the end of it if either party are unhappy with the outcome.
Hope this makes sense.