The Echo isn’t always sending recordings back to Amazon. All security teardowns I’ve seen agree with Amazon’s assertion that it only sends sound recordings after it is woken up with a trigger word.
Cory’s post is sadly missing the most relevant fact from the very murder investigation that he referenced. The police were unable to retrieve any data from Amazon, because the Echo products don’t send audio data to Amazon’s servers unless the wake word is spoken. It doesn’t matter how willing Amazon was to comply, they simply don’t have it.
Irony was still perfectly willing to lend a hand, however. His Echo Dot may not have proven to be a reliable IoT witness for the prosecution, but evidence was collected from his smart water meter. He allegedly murdered his victim about 1:00 AM or so, and around 3:00 AM, his water meter showed the anomalous use of a hundred gallons of hot water. The investigators claimed he used the water washing up the crime scene.
Moral of the story: if you’re about to be murdered, no matter where you are, loudly say “Alexa, Siri, Hey Google, Cortana*, I am being murdered!” Some nearby phone or audio device might pick it up.
* Yes, that’s a joke. Nobody has Microsoft phones.