Ths CVR was installed essentially to provide a record of cockpit sounds for use in the event of serious accident resulting in Flight Deck crew loss or injury. It was never installed as a 'spy in the sky' to monitor conversations after a normal flight, or indeed to investigate conversations after an incident when those involved are able to give their evidence afterwards. As far as I am aware, it is every pilots' personal right to erase the recording whenever he so wishes. I understand it does actually erase the loop.