A good investigator knows questioning someone directly can elicit reactions and lead to better detailed information.
Originally Posted by eccieuser9500
That's called a deposition. Completely different from interrogatories.
You don't even know how to ask the right questions in your own thread. What you seem to be struggling to ask is - why didn't Mueller depose Trump, i.e. question him directly under oath?
I could give you an answer to that one too, but why bother when you obviously don't understand the basics of our legal system?