[kolev]

Spying on you by default... A lot of people don't understand how much self-incriminating information there is in all that physical activity data. Imagine you're accused of committing a violent murder. And you own an iPhone. And you claim you were sleeping at that time. But your physical acitvity data shows otherwise.

[coralreef]

Wouldn't they need to decrypt the data in the first place? But perhaps that digresses from the point...

[r00fus]

The major problem is parallel construction. If the police can use this data - obtained illegally and surreptitiously using tools like accessdata or cellebrite to search for confirmation, they could extract a plea from you or find/manufacture other facts that do incriminate you or tear down your defense.