How did Linus know the answer to Benedict's question?

I've got two theories to explain how Linus knew the answer.

1. He researched the commission thoroughly hence was aware who Hal Lindley was, and that he had died. Considering this was Linus's main role in the heist it would make sense that he spent a lot of time studying his character and learning about other employees at the commission and how it's run.

2. Linus was not aware who Hal Lindley was and improvised on the spot that he had passed away to avoid anymore questions about Hal that he may not know. If you've seen Catch Me If You Can (2002), there's a scene where Leonardo DiCaprio's character was asked about the teacher's dog's name. Since he hadn't actually been to the school, he lied and said the dog died to avoid any more questions on the matter that he couldn't answer. Linus may have been doing something similar.

If I had to pick, I'd say Linus just already knew who Hal was. Considering Hal was someone that Benedict knew, it's likely he would be aware if Hal had died. He probably just asked to try and catch Linus out in a lie. If Linus didn't know who Hal was, he probably would have just said he hadn't worked with him before, rather then say he passed away. So I think it's safe to assume that Linus had an in-depth understanding of the commission and had researched what had happened in the past two years, that he claimed he'd been there for.

Hal Lindley was the cover/name used by Bobby Caldwell during a con he pulled while at the NGC. 'Hal Lindley' died when the con was over.

I have been holding this in my brain for many years. I never found anywhere to write about it until now.