"Recent experimental results" show that chemical compounds in a mouse's "urinary" scent produces an "odortype" that's unique to each individual rodent, Darpa observes in its original solicitation for the project. "Although experimental data for humans is far less quantitative," the agency is hoping that a similarly "genetically determined," "exploitable chemosignal" can be found in people, too.
Once that marker is found, Darpa's proposed 2007 budget notes, the agency wants to know what "the impact of non-genetic factors (e.g., diet, stress, health, age) [have] on the signal." That could help figure out how to "robustly extract" the signal "from a complex and varied chemical background."This is by no means a new concept: the Stasi, the East German secret police, kept scent samples from known dissidents and suspects. Though the Stasi used an almost Victorian low-tech method (swabs of cloth in glass jars), whereas this, if it works, will take the technique into the 21st century, by digitising scent signatures. Then miniaturised sensors, dropped by the trillion from unmanned drones over Waziristan or Venezuela or whatever the future theatre of war may be, can not only phone home if they find Osama (or whatever enemy the state of the day—or, indeed, any non-governmental agency with the resources to deploy such a system—needs to hunt down), but report back on what he's been having for dinner and what state of health he's in.
Coupled with the sort of data-mining/pattern-matching that gives PNAC technocrats woodies, the possibilities are even broader. What if there are certain molecular aspects of one's smell signature that correlate with interesting aspects of one's ideological beliefs or behavioral tendencies (for example, whether one is a devout Wahhabi Muslim, or a vegetarian, or possessed of an unusually high sex drive or a propensity to anger). A fine mist of sensors could find potential jihadists before they ever strap on a bomb; as it could well find other people worth keeping an eye on, in the interests of national security, global stability, public order and/or the status quo. It's the old SubGenius idea of "whiffreading", updated for the post-1998 and post-9/11 Homeland Security Age.