This was something that I was very worried about when I first started doing audio interviews. To have to get a signed release for every interview you do with an expert can really bog down the process. Do radio and tv stations get a sighed release for every person they interview? Does a reported who talks to people on the street have to get a signed release? NO.
It is not necessary to get a release signed by each interviewee in my opinion. Consult with your attorney if you need depending on what you are going to do with the interviews. Let’s say that you wanted to develop a series of interviews and package it and try and sell it off to a big network or sell it for hundreds of thousands of dollars or something like that. I think it may be a good idea. I guess it doesn’t take that much effort but it would probably be a good idea.
I don’t think it’s necessary to do it at the level that I’m doing it. I think an oral contract is good enough but maybe something like that if you’ve compiled a series of interviews and let’s say you’re publishing a book and it’s a big publisher I think they are going to want to know that you have the rights to publish this book and use these interviews. So in that case it may be a good idea to cover your bases. A good attorney in your area could probably help you out with that more than me.