When you are trying to craft a quality story structure, you are going to go after the individual drives of the characters. In this, you may have to spend extensive amounts of time, even having them open up personal things like legal and medical records.
If this is where you would like to go with your film, it is important to suggest it casually at first before requesting it openly. This way the idea is in their mind, and, through a cordial relationship, you can gain a stronger sense of trust between you. Once it appears as though the bond is strong enough, ask them to begin looking over some documents.