Any audio recordings are illegal unless you get the others consent.
I have seen people take answering machine tapes to the TV courts
(I guess answering machine tapes are okay)
the Judges all say they will listen to the tape but they can not base the weight of their decision on the tape.
I believe it is a federal law, but some states allow it under certain conditions I think.
"Can We Tape?"
click on the state-by-state and then click Maryland.
Video taping is okay in some states but with guidelines.