Keep an eye on Ars Technica in the next week or two, and also take a look at this article: http://arstechnica.com/tech-policy/2016/12/police-ask-alexa-did-you-w

Keep an eye on Ars Technica in the next week or two, and also take a look at this article: http://arstechnica.com/tech-policy/2016/12/police-ask-alexa-did-you-witness-a-murder/ http://arstechnica.com/tech-policy/2016/12/police-ask-alexa-... TL;DR: The Echo uploads audio for cloud-based recognition when it detects voices, but it's not clear if or how long Amazon keeps that. The Echo also has its internal audio buffer which is used for that detection, and in this case the police were looking for any audio that might have been retained in that buffer in the time period before the device was disconnected during the investigation.