(this will only work for admins since it involves the /invisible command)
I don’t know why I haven’t told people this before. But this happened to me once when I aimbotted (long long ago).
There was an admin who was invisible. He stood close by me and I shot at him (because the ESP showed his position). At first I was like “What the heck there is no guy there”
But then I realized who it was and was like WOAH.
Just a lil’ story and tip.
O.o
Well I used to. Even managed to escape getting GBLed.
I don’t anymore, my ratio can tell you that 
Given you aren’t an administrator, you can go in spectator and hug up to the person yourself. Snaps are quite easy to catch.
Like Korakoff said, the ESP shows you spectators posistions(I’ve used aimbot on my server), but you cant snap at them. So it’s pretty obvious when someone keeps looking at you while you spectate.
Yes that works. Tried it myself.