"When somebody is in this situation," says Duane, a Harvard Law graduate whose 2008 lecture on invoking the Fifth Amendment with police has been viewed on YouTube nearly 2.5 million times, "when they are involuntarily summoned before grand jury or before legislative body, it is well settled that they have a right to make a 'selective invocation,' as it's called, with respect to questions that they think might raise a meaningful risk of incriminating themselves."
In fact, Duane says, "even if Ms. Lerner had given answers to a few questions — five, ten, twenty questions — before she decided, 'That's where I draw the line, I'm not answering any more questions,' she would be able to do that as well." Such uses of selective invocation "happen all the time."