This is beginning to sound like the Clinton era "protective prosecution" where the DOJ would investigate people to keep them from testifying to Congress. I say embarrass and burden the hell out of Lerner. Also, since the 5th amendment doesn't protect her from testifying against other people, ask her lots of questions about what other people in the IRS did or knew. She'll probably try to weasel out of answering because by knowing others acted illegally and not reporting it she may have also committed a crime, but at least make her squirm publicly.
Once she pleads the 5th in one question she’ll have to plead it on all of them.
“Also, since the 5th amendment doesn’t protect her from testifying against other people, ask her lots of questions about what other people in the IRS did or knew. She’ll probably try to weasel out of answering because by knowing others acted illegally and not reporting it she may have also committed a crime, but at least make her squirm publicly.”
That is a common tactic in this sort of thing. Especially if her testimony does not then line up with the statements of other people who have been called. It is very hard for leftist to get their story straight because they are not used to being challenged. Catch them in perjury then offer them the chance to come clean or spend some serious time in the Federal slammer