[Snarf]

All admins should (and probably be required to) record demos of their play sessions, not the reverse (as that's really the only "proof" that would be definitive).

If someone is such an abusive admin it shouldn't be too hard to press a hotkey that records a demo, I have record bound to h and stop bound to i for this reason. When I played I would record demo's and just stop the demo before map change if I didn't have anything noteworthy happen. This whole process took me about all of two seconds maybe 10 more if i had to rebind h because I did happen to catch something.
But I was doing it for recreational purposes, admins shouldn't be on trial 24/7. If you can't trust your admins to behave without being under video surveillance they probably shouldn't be admins to begin with.