However. Let me straw man a bit here.
In the case of, say, someone being murdered with "a 16 inch double ender" at a themed orgy... Well, let's just ask google for anyone who has searched for an appropriately inclusive set of terms in the past 3 months. It's logical that someone who gets flagged in this data set could be the culprit right?
Gosh I sure hope none of the data gets leaked or misused in any way by the fine upstanding people who get access to it.
It's a case of balancing two rights - the right to privacy, and the right to life, to not be murdered. An absolutist stance on one would damage the other, and so we give judges the power to make decisions.
The whole point of having judges is to have upstanding and reasonable people we trust for this purpose, so we don't have to explicitly deliberate about every edge case before it happens.
And yeah, I don't trust the police with my data but I am reassured by the limited time and geography in their request.