Long story short, I have a horrible relative that says things to me that they then deny saying to the rest of the family leaving me to look like I'm making baseless acusations.

Ideally, I'd love to shove a microphone in their face when they are in my residence and tell them "anything said in this house will be recorded, if you don't like it you are welcome to shut your mouth or leave." This would certainly avoid any surreptitious recording which is explicitly illegal.

Does it make a difference if I'm just going to play the recordings for the family to prove that this person becomes verbally abusive when nobody else is around? It is not currently my intent to use the recordings for anything else.

Or, would I be legally obligated to stop any recording if they explicitly state that they do not consent to being recorded?

Sorry for any vagueness, I wanted to avoid a lengthy history of family drama.