Just when it might appear that the IRS scandal cannot descend any lower, it has taken on the distinct odor of the Watergate cover-up with the most politically convenient computer crash in history. Naturally, the Obama administration waited to release the damaging news on Friday afternoon to minimize its impact. The alleged crash means the federal tax agency can only produce copies of emails to and from Lois Lerner and other IRS employees for the period January 2009 to April 2011. So all emails Lerner sent during that period from her official IRS account to anybody outside the agency -- like the White House, the Justice Department, the Federal Election Commission, Democrats in Congress or political activists in liberal nonprofits -- have vanished into a digital black hole.

The period involved just happens to be when Lerner and others in the Obama administration and key Senate Democrats hatched and began carrying out the targeting and harassment of Tea Party and conservative nonprofit applicants during the 2010 and 2012 campaigns. Included in the targeting and harassment was the illegal sharing of confidential tax information with individuals outside of the IRS. It also involved an attempt to gin up a political prosecution of doubtful merit by the Department of Justice against selected critics of President Obama.

Rep. Charles Boustany, chairman of the House Ways and Means Committee's investigations subcommittee, didn't buy the IRS explanation, saying "the Obama administration repeatedly claimed we were getting access to all relevant IRS documents. Only now -- 13 months into the investigation -- the IRS reveals that key emails from the time of the targeting have been lost. And they bury that fact deep in an unrelated letter on a Friday afternoon. In that same letter, they urge Congress to end the investigations into IRS wrongdoing. This is not the transparency promised to the American people. If there is no smidgeon of corruption, what is the administration hiding?"

Good question. President Nixon's secretary, Rose Mary Woods, claimed to have accidentally erased an 18.5-minute segment of a key White House tape recording of Oval Office conversations. She went to her grave in 2005 without disclosing what was said during those 18.5 minutes. Her silence may have saved Nixon from criminal prosecution. Recording technology was not sufficiently advanced in 1973 to enable recovery of the erased voice data on the recorder's tape.

Forty years later, the situation may be quite different. For that reason, House investigators should demand every IRS computer network record, as well as the emails of every employee in the relevant departments. Recorded interviews should be conducted with those employees as well.

Computer crashes do not inevitably and always destroy all data on a hard drive. Computer networks typically have backup systems to prevent such data loss. And system administrators record the circumstances surrounding crashes for future reference and for determining how to prevent their recurrence. The IRS can claim it was unable to find Lerner's emails due to the crash, but the smart money says the NSA can do it.