. . . . today I got a letter of intended prosecution they do not state anything about evidence or that they can see if the tickets have been used just that I have to return a form stating my version of events. . . .
. . . What rights do I have? How can I prove I’ve never used the tickets before?
The 'rights' you have are those of anyone suspected of a Criminal Offence - the automatic right of being innocent until proven guilty - that proof of guilt must be to the standard of 'beyond all reasonable doubt' - the right to have the accusation tested in a Court by cross-examination of the witness presenting that Evidence against you - to be represented in Court by a legal professional - to have the Prosecution's Evidence against you 'put to proof' - and, if you fail to establish your innocence, your right to Appeal.
How do I know they haven’t tampered with the tickets
Well if you really had any reason to believe that was true, then you could have your own forensic analyst examine them and provide Evidence as an expert witness; nut it beggars belief that any Train Operating Company would have the inclination, time or justification to fabricate evidence - surely it is clear to you that there are thousands of passengers travelling without having paid their to investigate, without having to add the perverse concept of inventing / fabricating more of them? That really isn't a line of thought worth your concern!
. . . . . they may decide to prosecute you regardless of the quality of their evidence and hope that you plead guilty or, if you don't, that the magistrates believe their evidence more than your defence.
I really cannot see any Company bothering to put weight on a "hope" that a suspect will plead Guilty!
They will apply the Full Code Test, in which the basic first test must be to confirm that the Evidence, in itself, is likely to be persuasive of Guilt to the standard of 'beyond reasonable doubt' and then if it does, and only then, the 'public interest test'. Most railway fare evasion incidents are likely to pass the 'public interest test'.
It would be worth speaking to a criminal prosecution (ideally a railway prosecution) solicitor if you find yourself in this situation.
No. NO.
NO!
Save yourself 4 grand. It would be a pointless waste. Just speak to any local law firm who deals with everyday Criminal Defence work. DO NOT SEEK OUT A CRIMINAL PROSECUTOR. AND DO NOT GO HUNTING FOR ONE OF THE TINY NUMBER OF SPECIALIST RAILWAY PROSECUTORS. That would be a very expensive and pointless use of your resources and I can't imagine why anyone on here would give advice like that to someone in your position which would put you in such a disadvantage. That sort of 'advice' simply shows this forum to be an unreliable source of personal opinion.
That's not really relevant to the (alleged) fraud, but is it a standard procedure to ask another passenger for an opinion on the ticket validity???
It is not. But it can be helpful to, either, have another witness if a statement is made which might require corroboration, or more likely, if it considered at the time that a confrontational incident might be defused and contained in a more reasonable and constructive discussion by introducing a third party perspective on the facts.