IANAL but my reading is that by transmitting chat messages you are generating potential evidence so discarding those is destruction of that potential evidence.

IANAL but my reading is that by transmitting chat messages you are generating potential evidence so discarding those is destruction of that potential evidence. Presumably this does not apply to audio-visual real time communication as you're not transmitting entire messages but fragments in real time that don't convey any information by themselves. Sending back and forth recorded audio messages OTOH would presumably produce potential evidence. Sending each letter as it is typed presumably would not. That said, usually these things are ruled based on the spirit of the law as much as the letter of the law so trying to game this by working around technicalities would likely be considered ... bad.