If he lived in New York or New Jersey, he could legally record the other person without telling them, and it would be admissible.
In states like FL, CA, PA, DE, IL, WI, NH, MA, not only would it be admissible, the person doing the recording would be breaking the law.
Now an attorney recording a client ANYWHERE and then releasing it seems like grounds for disbarment to me, but I don’t know how that works.
i also believe in the state of NY if there are three people on he conversation at least two must be aware if the conversation is being recorded...