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.
(..) you're gonna have to speak from the heart and not make it about you. Well, that's just impossible. You know what these things are capable of. Even if you lose the election, another one like you is gonna rise up and take your place. J.J. Abrams has seen to that. Don't you get it, Randy? (..)2016 TvShow: South Park Title: Fort Collins Season: 20 Episode 6