Wow. Rough crowd.
In my working days we had upwards of 100 journeyman electricians in our plant and one thing that I learned from them was that if there was any doubt you checked it with a meter. A transformer with no power to it isn't a problem but one with wires going to it needs to be checked with a meter. Anything that may have capacitors or batteries must be checked. Just assuming that something is dead is a good way to die.
On that note I really wish my meter had like a 6vac output that I could touch the probes to and double check my meter functions. Assuming a zero on my meter means no voltage is equally deadly.
I once worked on an electrical panel that had a main feed, and two separate breakers that were live from the load side from two different services. I shut the whole building down and still had power at the stupid panel.