He is not 'capable of' making those medical decisions himself. [=he cannot make the decisions by himself because he cannot think clearly, he is too sick, etc.]
I don't believe that she's 'capable of' murder. [=that she is the kind of person who could murder someone]
She is one of the most 'capable' [='skilled'] and versatile actresses in Hollywood.
(..) It could be dangerous. Oh, darling. Not to worry. Trust me. I may be a bit rusty, but I'm perfectly capable of taking care of myself. I congratulate you, Chief, on your excellent facilities. Of course you understand that my visit here must be of the utmost secrecy? Of course. My department will do (..)1975 The Return of the Pink Panther