Earlier quoted context omitted.
Isn't it a good thing to record data that helps solve a murder? The police are still getting it with a warrant and presumably from physical access to the device, so it's not the same worry as bulk monitoring.
its a fine line. There is a great fear of false positives from such inference. Let us imagine for a second that there is a legitimate reason for that water use that he doesn't wish to disclose because it would incriminate him for something else? Hypothetically speaking if you were doing some grey-hat, "illegal" probing/hack at the time of a murder the police question you about; admitting to your actual activity could…
Take criminal cases where they find drugs in your system and use that to make it look like you're more apt to commit said crime.