[Dah00n]

Why do you need someone who worked with him to attast it? Engineer is something you go to school to become, not something you become because you have money or workers. Either he have an education as an engineer or he isn't an engineer. Giving yourself a title in your own company doesn't make it so.

[iso1210]

In many countries, Engineer is a protected status job title. In the US I believe "Professional Engineer" is protected

In the US, going to school to become a Graduate Engineer does not make you a Professional Engineer.

[fastball]

You definitely don't need formal education in order to be an engineer.