In the wake of the news that a computer crash destroyed over two years’ worth of Lois Lerner’s emails, House Oversight Committee chairman Darrell Issa on Tuesday subpoenaed her hard drive. Unfortunately, according to a source in the IRS’ IT department, that subpoena is unlikely to turn up much.

As a matter of practice, says the source, the IRS discards damaged hard drives after wiping them of all data. ”If we can run them, we have to wipe them,” he says. If they will not run, the agency destroys them completely by magnetically degaussing them.

In both cases, the damaged hard drives are disposed of. “You’re not supposed to keep them around,” the source says. “You destroy the data.”