Since 2016 when I posted my comment on this thread, I received many request just like yours. First, in most country it is illegal to record people without their knowledge. Be carefull ! Second, I ain't considering any request like I did then, I've waisted so much time explaining people that audio is like a cake, you can't extract the eggs once it's baked. Unless you put the eggs on top and didn't mixed them lol.. If you have a legal issue, hire a lawyer. Most will have access to forensic firms that will analyse the recording. But don't expect magic like you see in the movies. They can't extract the sound of locusts behind an atomic bomb.. not they can't !