There is a database which tracks patients' narcotics use which is monitored by physicians, pharmacists, and law enforcement. Narcotics with a proper prescription aren't illegal, but in an effort to lower abuse etc it's tracked.
So I was thinking that Holmes has been collecting ammunition, body armor, and explosives for months and how if there was some way certain items are reported to a central database which can flag a person go up when various combinations of items or quantities of items are purchased and analyze buying behavior of people, groups of people, and all sorts of filtered ways, then maybe it could prevent stockpiling and also be a tool to fight terrorism.
I haven't thought it all the way out and I know it'd be strange to ring up ever bag of fertilizer but it'd just like how narcotics are reported. Maybe some more sophisticated software could be developed to do more analyzing and such but these are just my primitive thoughts about how to prevent stockpiling by even the most clever of criminals.
Debate questions: do you think creating a database tracking and analyzing buying behaviors is an infringement of any sort? Do you think it would be helpful to prevent massacres such as these from happening and perhaps foil other terrorism from being actively plotted?