The way it works, I'm afraid the answer is neither. They were asked to come for an interview and they agreed to come. That's usually the case. Very few people actually volunteer for an interview. That's how it goes.
We basically review the documentary evidence. We determine what more information we need from anyone, and we call witnesses. I have the power to subpoena people. I have not had to issue any subpoena since my appointment back in early 2018. They did come voluntarily, but as a result of a request that we had made of them.