According to civil rights attorney Alan Dershowitz, IRS scandal figure Lois Lerner’s Fifth Amendment plea could backfire badly on her.

“You can’t simply make statements about a subject and then plead the Fifth in response to questions about the very same subject,” the renowned Harvard Law professor said.

“Once you open the door to an area of inquiry, you have waived your Fifth Amendment right . . . you’ve waived your self-incrimination right on that subject matter.”

He said the fact that Lerner went ahead with her proclamation of could be considered malpractice on the part of her attorney — although it’s possible she overruled the advice she received.

“It should never have been allowed. She should have been told by her attorney that the law is clear, that once you open up an area of inquiry for interrogation, you have to respond,” he said.

“Now she may have made a political decision that it’s worth it to take the risk . . . That’s just not the way the law works. It may be the way politics works . . . but she can’t invoke the Fifth.”

Dershowitz says Lerner could even be held in the Congress jail.

House Government Oversight and Reform Committee Chairman Darrell Issa is reportedly considering recalling Lerner to testify, after she refused to testify Wednesday.