IRS head returns to Capitol Hill to face questions about 'IRS obstruction' on lost emails

The head of the IRS is returning to Capitol Hill to face skeptical lawmakers with questions about lost emails.

Ahead of Monday night's hearing, the House Oversight Committee has asked IRS Commissioner John Koskinen to address a series of technical questions about the agency's email system and its policy for retaining official documents.

The title of the hearing suggests that committee Chairman Darrell Issa already has reached some conclusions. The hearing is called, quote, "IRS Obstruction: Lois Lerner's Missing Emails."

The IRS says that in 2011, it lost an untold number of emails to and from Lerner, the former head of the division that processes applications for tax-exempt status. Issa's committee is investigating the handling of applications from tea party and other political groups.