What does "case closed" mean here?

Rebecca

"Case closed" is a casual expression used to mean that something is final or not available for further discussion. It originated in the courthouse, when judges banged their gavel on their desk to signal a final judgement. Similar expressions include "end of discussion." Ex: She cheated, they got divorced. Case closed. Ex: We installed a hidden camera and discovered it was our dog stealing the socks, not a thief. Case closed!