To my understanding, these smart speakers only phone home when you say the keyword, right? They aren't storing or sending everything they hear throughout the day. So the cases where this could be abused by police has to be small. Seems like it would likely be used to verify that someone was home when they said they were because they asked Alexa a question at that time.
In other words, I don't think Amazon ever receives the "wrongthink" Alexa hears, unless you say it directly to Alexa.
I'm fairly sure there have been multiple stories about smart speakers sending things they hear without the keywords.
Well, that's a depressing sentence to read. The vultures may be circling, but Firefox isn't dead yet.