"He may be mistaken about what he has seen."
I have some difficulties with getting the sentence above.
What does "to be mistaken" mean? Is it passive voice or what?
However, this can be a passive construction. "He may be mistaken for a robber if he wears a mask" = "Someone may mistake him for a robber if he wears a mask".
"I'm mistaken" means "I'm wrong".
"I'm mistaken for an alien" means "Someone has mistaken me for an alien."
The context should signal whether it's a passive construction or an adjective.