According to Osho, you shouldn’t try to certify sadhus at all: sainthood is a private affair, and public worship breeds fakes. Drop special respect and most impostors vanish. If you must look, the authentic does not imitate, breaks patterns, is the same in public and private, and lives an experiential sense of the divine—whereas the false performs for followers.
Don’t judge or worship sadhus; real ones are the same everywhere, while pretenders act holy only when watched.