Signal processing en masse
You have a subject that is suspected of a crime, but they have taken steps to prevent the usual tracking.
He had no cell phone.
He had no electronics at all.
He traveled in an antique car with no electronics.
He avoided cameras.
There is literally no known method to tie his to the crime.
You create a new method.
You use existing cell phone tower signal recordings.
You use millions of processors, drives and billions of hours.
You create maps of where this person was based on his impact on the signals in the records.
You trace his route back.
You prove he was there.
You prove he did it with the mountains of data that was otherwise useless.