Based on a conversation with John Ralston:
Adapting one's interviewing style for evidence collection. I think the idea is to help elicit specific answers of use for evidence collection, and to help a lay person ask questions useful for evidence. There is a section on interviewing in the Dermott's Human Rights Investigation manual.
Styles do differ depending on what is being sought, and the kind of detail and linking detail needed; for example, a journalist typically doesn't need to account for someone's time, nor needs the kind of detail evidence requires.
He mentioned this in relation to police: they often have trouble with interviews because they assume their authority will elicit answers.