I think your memory is mistaken. Amazon will give up recordings when legally obligated to do so, because that’s the law. They can’t choose to ignore the law.

However, Alexa and similar devices don’t actually record everything. Amazon doesn’t get a recording of everything the devices hear. They have to be triggered by the wake word (or possible a false positive).

Here’s a case where the Alexa command was used as part of the case, though it didn’t have recordings of the actual crime: https://www.dailymail.co.uk/news/article-11899217/Murderer-j...