As ridiculous as it sounds, making people sign their lives away is a GOOD idea! Several reasons come to mind...
Imagine you're leading an investigation into a home. Once you're finished, you glance over to one of your group chatting it up to a "reporter" from a local newspaper about EVERYTHING that happened... according to them. Imagine if you gave your SOLEMN word to the person who reported the incident that you would maintain their anonymity? Imagine how much jail time you'd have to do if you followed what would be the obvious course of action you'd WANT to take with this team member...
Next, you head out to an abandoned factory where "things" have been happening... You get the permission of the owner and you're ready to rock WHEN one of your team slips on a set of stairs and WHAM! One broken leg. GUESS WHO'LL THEY'LL BLAME!?!?
So, in the interest of saving face and a possible court date, get your team to sign a non-disclosure/waiver before heading out. Not only will this protect you but will also assure the person that has agreed to let you come out that there will be no ramifications from allowing you to do your thing.
An example of such a disclosure would be...
DATE: ______________________ (Needless to say, this is why ALL your team MUST be legal adults in your neck of the woods!)
I, ___________________________ understand that all information pertaining to and gathered during the investigation of ________________________________________ will be kept in the strictest confidence and that I will not use this information for my own uses or any other organization's purposes nor will I discuss the events/information gathered with representatives of any media without first consulting and getting written authorization from _________________________.
I also understand that I am responsible for my own belongings and safety and realize that any loss or injury that occurs is my own fault and will not hold _________________________________ responsible.
I have read the above and understand fully my obligations.