Qualified Person, per the NEC

From the National Electrical Code (NEC):

Qualified Person. One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received Safety training to recognize and avoid the hazards involved.

FPN (Fine Print Note): Refer to NFPA 70E®-2004, Standard for Electrical Safety in the Workplace, for electrical Safety training requirements.

(This definition, and the difficulty of actually proving qualification, was one of the primary driving forces behind the formation of the ETCP and associated certifications. Right now in North America, the most unambiguous proof of qualification in the entertainment industry is an ETCP certification.)