Hey I just figured out how get around this law we have in California that it it not admissible in court as testimony against one opponent.
Just bleep out the the parts of parties that would object to it use in a case against them and let the willing parties voices be made clear that secretly made the recording could answered after being offered as evidence and latter questioned as to what was being said that made him respond with certain verbal expressions and thus use such testimony in a court of law for his defense against his oponent in law,. I think it could work. Why throw the complete tape out as testimony in a trail when there are those that feel it is their right to be heard and the other opposing power be bleeped out in harmony with the laws or intentions of the law for public good.