> What tools do you think law enforcement has to further narrow this down?
Further cross-correlation of more data. Have the farmers ever even been to the same town as where the bomb was detonated? Were they there that day? Do they have any apparent motive? What's their alibi? You still have to prove a criminal case beyond a reasonable doubt, so all the points you're raising about alternative explanations for such searches are exactly the things the defense would raise, and why police don't use this data collection as evidence, but to focus the search from 100,000 people to 1,000 people.
It's probably worth thinking about it that way: absent this data, police have to assume everyone at the mall might be a suspect, so the pool is 100,000 potential bombers, not 1,000. What's the success rate on guessing 1/100000?
Further cross-correlation of more data. Have the farmers ever even been to the same town as where the bomb was detonated? Were they there that day? Do they have any apparent motive? What's their alibi? You still have to prove a criminal case beyond a reasonable doubt, so all the points you're raising about alternative explanations for such searches are exactly the things the defense would raise, and why police don't use this data collection as evidence, but to focus the search from 100,000 people to 1,000 people.
It's probably worth thinking about it that way: absent this data, police have to assume everyone at the mall might be a suspect, so the pool is 100,000 potential bombers, not 1,000. What's the success rate on guessing 1/100000?