Under the EASA requirements:
ORA.ATO.110
(c)Theoretical knowledge instructors shall have:
(1) practical background in aviation in the area relevant for the training provided and have undergone a course of training in instructional techniques; or
(2) previous experience in giving theoretical knowledge instruction and an appropriate theoretical knowledge background in the subject on which they will provide theoretical knowledge instruction
AMC1 ORA.ATO.110(c)
Theoretical knowledge instructors should, before appointment, prove their competency by giving a test lecture based on material they have developed for the subjects they are to teach.
The exact arrangements for the recruitment, training and checking of theoretical knowledge instructors in an individual ATO will be detailed in Part D of the Operations Manual and approved by the competent authority.