oki so best would be a demo in this case.
its made by type /record <demoname> in console.
before u must set "g_syncronousclients 1" but the console will thell u that too
when u have suspicion bout wallhack:
start the quake, enter "/r_shownormals 1" in console
then say /demo <demoname> in console, it will play it, showing parts from the player, even if hes behind the wall.
btw: please post the demo in forums, then others can see and discuss.
btw2: short demos are good demos
btw3: i wrote here some bout demos in mine server. this is not mine server, but im sure that many things are helpful. to make it not boring, i added some funny animated gifs

klick
here to read