> There is no such thing as a certification that data was deleted. If someone presented such a thing I would assume they're trying to cover something up.
I have news for you. There are standards around data destruction [1]. Courts also order data deletion, to be carried out by forensic experts [2], who trace data in computer systems, and delete what is required, and certify accordingly. This can be done even in cloud-scale compute [3][4][5] - corporate systems especially have routine extensive logging and traceability that allows for this to be accomplished. The companies that I listed earlier specialize in this compliance capability.