This could be solved very quickly in my opinion, as there is first an individual who allegedly granted access to the perps to get into the offices of Price Waterhouse Cooper. Second, I would be surprised if there were not the most rudimentary security/surveillance system in place at the facility where the crime took place. Third, the flash drives used can be forensically dissected which can yield information on the system used to generate the data set on the flash drive.
Of course this presumes there is a real drive (no pun intended) to catch the perps, as this story does nothing but add ammo to the ‘Rat mee-mee about ‘Romney not paying taxes’, ad nauseum.
Perhaps Holder already received a copy of all of the returns for the last 20 years from the head of the IRS and couldn’t find anything really bad so decided to see how much mileage they could get out of some political spin.