it's been a while since i coded for sourcemod but something like...
Code:
...
if (
IsClientInGame(i) && // is in the game
IsPlayerAlive(i) // is alive
&& GetUserAdmin (i) != INVALID_ADMIN_ID // is an ADMIN
) {...
in the OnGameFrame call?
but surely someone's written a better plugin for this with a newer SourceMod version?