A warrant is required only as long as "voice assistant" technology "is not in general public use"[1]. Kyllo v United States created a bright-line[3] test that removes the warrant requirement to see "details of a private home that would previously have been unknowable without physical intrusion"[2] when use of the technology is normalized.
Note that this removes the warrant requirement in general, even if you personally don't own an Alexa/etc. The test is if the public expects audio in the home might be recorded and sent to a 3rd party. If the answer is "yes", then the police can use their own hardware to do the recording.
> The test is if the public expects audio in the home might be recorded and sent to a 3rd party. If the answer is "yes", then the police can use their own hardware to do the recording.
Honest question, are you an attorney or can one comment? I am not, but I don't read this opinion the same way.
The case referenced concerns using thermal imaging from outside a home to look inside it, which I guess makes sense then that if thermal imaging was super common maybe they would argue that its not a big deal to point one at a house by a cop, but thermal imaging is not common so it was ruled an unconstitutional search.
But you seem to have taken that as the police being able to enter a residence and install a transmitting microphone just because most people have transmitting microphones inside the house. There's a huge difference in a search that requires entering a home and one that does not.
SCOTUS actually seems pretty explicitly concerned in the text about technology eroding the expectation of privacy by the progressing deeper into a private residence without having to enter it, so that again implies this case was about technology being used to search a home without entering it.
Courts tend to look at precedent. Any lawyer taking a case in this area will look at the case in question and try to twist it to state their side.
This isn't to say courts will rule one way to the other, or that the courts won't change their mind, but a well reasoned opinion form a different court is powerful.
Note that re: Kyllo v United States, trust in any specific manufacturer is irrelevant. The SCOTUS ruled that use of a technology - not a product - requires a warrant when it is "is not in general public use".
The Kyllo case involved two federal agents that used their own thermal imaging camera to search a house for the presence of people and grow lights.
Glancing at the supreme court case, I'm not sure that observations that police officers can do from a public place have a good application to this area.
I think the public expectation part was specifically whether thermal imaging was too invasive and not an observation that the general public would make from the street.
Note that this removes the warrant requirement in general, even if you personally don't own an Alexa/etc. The test is if the public expects audio in the home might be recorded and sent to a 3rd party. If the answer is "yes", then the police can use their own hardware to do the recording.
[1] http://caselaw.findlaw.com/us-supreme-court/533/27.html
[2] Ibid.
[3] https://en.wikipedia.org/wiki/Bright-line_rule