To file a patent must I have a prototype? If not, who takes care of verifying if the invention really works?
The prototype, even though very useful in the experimentation phase, is not necessary for a patent application. In fact the application has a description, functionality, how to realize the object, as well as the drawings. The patent is granted according to the text and how it is claimed in the documentation, this being the only instrument of comparison and of decision taken into account by the examiner: even if there was a prototype, this would not be considered at all, bearing in mind only the text of the application.
On the second question, in practice, no one verifies whether or not the system works, unless a patent is applied for an object quite clearly impossible to make. Up to now, the only patent applications almost automatically rejected by the Italian Patents and Trademarks Office, are those related to the “perpetual motion” and relative devices allowing this motion. The examiner’s responsibility is to ensure if there requisites of patentability are met, and not to see whether it would be possible to make a certain object in a particular way, or if the invention permits to achieve the described advantages. This kind of “test” is usually done by the inventor with the prototype or, as in a specific case, by the company interested to produce the invention.
Therefore it is a good rule to ensure to plan an object in a functional way, and if there isn’t the possibility to make a prototype, then the functionality test should be postponed to such time when there will be some interest in its production.