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LMGTFY - Let Me Google That For You
For all those people who find it more convenient to bother you with their question rather than to Google it for themselves.bfy.tw
But just used that as one example of available listening tech.
I think LE subpoena of device information has to be tailored to a specific issue in the investigation. For example, location data can confirm or dispute where a person was, or a person's alibi. But the predicate for the seizure has to be laid out and cannot simply be a fishing expedition. I think police would have to first confirm that there's a relevant device and then get the warrant based on probable cause to search the device's data or recordings that they will obtain by subpoena to the device company (in cases of where the material is available that way, i.e. cloud or company servers).
I'm sure this varies by state and even by judge, but simply saying "there's a device in the house that may have recorded things Brian said to his parents" doesn't strike me as a proper predicate for a warrant.
However, I do know that some device and data companies have a law enforcement policy that doesn't necessarily require a subpoena. So that may be more accommodating.