Recording of any conversation without consent from others won't get though the court. Judge will dismiss this and will not present to the jury.
Same principle that happened recently in the court where police had secretly installed GPS on suspect's vehicle, that is without the vehicle owner knowledge. Court had struck down that because of two things, no owner consent, nor court consent. Now, if police want to plant GPS on suspect vehicle, police are required either to get permission from judge or inform the vehicle owner and get approval from him.
Witness does not require any approvals.
BTW glad to hear you had this work out with Co-worker. I would suggest that you let co worker you don't take this lightly and will take action if this happens again. You will get more respect afterwards.
Gee immediate supervisor got fired? It shows that company can't afford this and don't want happen again. Any legal involvement cost companies dearly.
