The key to witness interviews is to have a game plan before you start the interview. Don’t just walk in with a copy of the sworn statement and run down the sworn statement. Sworn statements are just starting points for you to start thinking about your case (they are also important later on, for impeachment). For witness interviews, you should have a list of things that you think this witness can help (or hurt) you with. You generated this list when you did your case analysis. Cover these items in your interview.
Be efficient. When you interview the company commander, find out what she knows about the offense; what she knows about the search and seizure issue; what she knows about the accused’s military character; what she knows about the impact on the unit; etc. Do it all at once. Don’t keep calling back because only later did you realize how else this witness impacted your case.
A witness statement is not a Shakespearean play. It is not a script, and witnesses will invariably suffer memory loss, alter their testimony (intentionally or unintentionally), or fail to report important information at some point in every case. Wise counsel therefore view prior written statements as merely the starting point for an interview; and then try to memorialize what they learn in the interview in a way that locks-in the witness to those facts.
The goal of CID and MPI is to close a case. The standard to opine probable cause is, by definition, lower than that of a contested criminal case. For that reason, counsel should never assume that investigators probed facts to a sufficient level of detail.