Legal Question: In A Criminal Trial, Could the Defense Subpoena The NSA?

Suppose you are a defendant in a murder trial. Your alibi could be proven if your now-destroyed emails could be produced. Could your defense lawyer subpoena the NSA to obtain the vital emails? They are your property, but now in government custody.

I wonder if NSA is protected by any sort of privilege. I would be shocked if its not.

I suspect the state secrets privilege would be invoked.