A.T. Robertson Commentary John 10:21

"Others said, These are not the sayings of one possessed with a demon. Can a demon open the eyes of the blind?" — John 10:21 (ASV)

Of one possessed with a demon (δαιμονιζομενου). Genitive of present passive participle of δαιμονιζω. They had heard demoniacs talk, but not like this.

Can a demon open the eyes of the blind? (μη δαιμονιον δυνατα τυφλον οφθαλμους ανοιξαι; ). Negative answer expected. Demons would more likely put out eyes, not open them. It was an unanswerable question.