mum2taylor what's the disciplinary for? And why do DPs employers need access to his medical records to determine the outcome? That sounds very bizarre.
I would agree that other than in exceptional circumstances an employer should wait until someone is fit to work before conducting a disciplinary hearing. If an employee is not fit for work they wouldn't normally be fit to properly participate and represent themselves effectively anyway.
It is good practice to visit members of staff who are off sick for significant periods, to see how things are going, keep them in touch with the workplace and discuss how best to get them back to work, or what support is needed.
However it is not good practice to visit an employee's home to discipline them! I hope they followed all the required steps as set out by Roskva. Even if they did, should DP not be happy with the outcome, he should definitely appeal it.
In terms of accessing medical records generally, there's no rule about when it can be done. An employee must give permission, however. It's fine not to give permission, but consider longer term whether it might be detrimental to refuse permission. Difficult to say without knowing what they want to know and why, but if they need to check that he was genuinely sick, for example, obviously it's in DP's interests to let them see.