Under the Federal Rules of Civil Procedure and legal precedent, once the suit was filed the IRS was required to preserve all evidence relevant to the viewpoint-discrimination charge. That means that no matter what dog ate Lois Lerner’s hard drive or what the IRS habit was of recycling the tapes used to back up its email records of taxpayer information, it had a legal duty not to destroy the evidence in ongoing litigation.

In private white-collar cases, companies facing a lawsuit routinely operate under what is known as a “litigation hold,” instructing employees to affirmatively retain all documents related to the potential litigation. A failure to do that and any resulting document loss amounts to what is called “willful spoliation,” or deliberate destruction of evidence if any of the destroyed documents were potentially relevant to the litigation.

At the IRS, that requirement applied to all correspondence regarding Z Street, as well as to information related to the vetting of conservative groups whose applications for tax-exempt status were delayed during an election season. Instead, and incredibly, the IRS cancelled its contract with email-archiving firm Sonasoft shortly after Ms. Lerner’s computer “crash” in June 2011.