at which point does the defence lawyer show to the sherriff and the procurater fiscal any supporting evidence they have for his client. and when does the PF need to show evidence against after initiall charging
As far as I know, the Sheriff knows nothing about anything before the trial. I don't know if the defence discloses to the PF, but I do know that the PF gives all statements to the PF before the trial.
It is called "Disclosure". The Prosecutor has to disclose all the evidence they wish to rely on in court, along with witness statements photographs etc. This is to give the defence a chance to refute the allegations and formulate cross-examination lines before the court date.