When we received him in our interview, we asked him to tell us a bit about his past projects, what he liked, disliked, etc. He didn't talk much and it took us a lot of questions to dig up helpful things.

Then we asked a couple programming related questions and he bombed them all. He couldn't put an algorithm into words, write code that compiles or gives the proper results. Our interview programming questions start very easy and we slowly iterate by adding more constraints that shows if a dev has a deep knowledge of the language and framework.

I have a feeling like this developer was good when he's working alone on a project with no one to talk to. He would have never fit in our company culture and we couldn't evaluate his skills in an interview.