SBF seems like the kind of big mouthed overconfidently stupid smart person to walk right into that. He certainly has a lot of content out there on the public record for them to cross check his recollections against!

Interesting. How would someone prove this?

Wait for him to publicly say something stupid about it that admits guilt.

By coming at the question from another direction step by step leading the person into a trap.

But memory is unreliable, specially if you're under pressure. This is seen for example when taking exams, some people might just completely forget what they were just studying

Is this really a crime?

Yes. If you don’t want to answer because it might be incriminating, then you have to assert your fifth amendment privileges; you can’t lie and say that you don’t remember.

Do people get prosecuted for perjury after getting a guilty sentence like that? I imagined the most important consequence of saying "I don't remember" is whether the jury finds you credible.