In addition to Wireshark, we have pretty strong legal evidence. When Amazon was made to provide whatever recordings they had from the Echo in that homocide case

In addition to Wireshark, we have pretty strong legal evidence. When Amazon was made to provide whatever recordings they had from the Echo in that homocide case, they said they only record the commands given and don't have an always-on microphone. If that was not the case, Amazon would be committing a major crime to cover up such a feature. Disclaimer: work for AWS, not affiliated with Alexa or Echo.