Lois Lerner, the director of the IRS division that singled out conservative groups, is expected to invoke the Fifth Amendment Wednesday when she appears before the House Oversight and Government Reform Committee, Fox News has learned.

That means Lerner, head of the exempt organizations division, probably won’t answer any questions on what she knew about IRS agents going after Tea Party-related groups. That also means she probably won’t say why she sat on the information for so long before it became public.

Lerner’s attorney, William Taylor III, asked committee Chairman Darrell Issa, R-Calif., in a letter if she could skip Wednesday’s hearing since she would be pleading the Fifth.

Taylor argued in the letter that forcing Lerner to appear “would have no purpose other than to embarrass or burden her.”

Late Tuesday, the House oversight committee released a statement saying Lerner was still under subpoena and would be required to appear in the morning.

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“Chairman Issa remains hopeful that she will ultimately decide to testify tomorrow about her knowledge of outrageous IRS targeting of Americans for their political beliefs,” committee spokesman Ali Ahmad said in a statement.

Other former or outgoing IRS officials have already testified, and will continue to give their testimony on Wednesday. But Lerner, who is the official who first acknowledged the IRS program, has faced significant scrutiny.

Since the Department of Justice has launched a criminal investigation into the IRS scandal and the House committee indicated it would question Lerner about why she provided incomplete information to the committee at least four times last year, Taylor wrote that his client would be invoking her Fifth Amendment right against self-incrimination.

The House committee is also scheduled to hear from Deputy Secretary of the Treasury Neal Wolin, among others, as the search for someone who will claim responsibility continues.

On Tuesday, outgoing IRS Commissioner Steven Miller, was back in the hot seat as he testified for the second time in two weeks on Capitol Hill.

Miller expressed regret for the agency’s decision to use a planted question to go public with the IRS’ practice of singling out conservative groups.

It was one in a series of missteps that have not only publicly marred the reputation of the IRS, but also called into question what the White House knew about the scandal and when they knew it.

“We’re not looking for people to be evasive, but we want people forthright and straightforward with us,” Rep. Joseph Crowley, a Democrat from New York, told Fox News.

While Crowley did not go so far as to say Lerner should be let go, he did say, “the bottom line is that you cannot lie to Congress, be evasive or mislead. You must answer the question and not mislead Congress.”

Separately, two Tea Party-related groups filed lawsuits against the IRS this week.

On Tuesday, Texas-based True the Vote claimed it was unfairly targeted by the IRS and demanded in court documents the government admit its mistake, grant the group tax-exempt status and pay for damages totaling more than $85,000.

On Monday, the NorCal Tea Party Patriots filed the first federal suit against the national tax agency. Like True the Vote, the northern California group says the IRS violated its constitutional rights when it held up its applications for tax-exempt status.

The NorCal lawsuit, filed in the U.S. District Court of Cincinnati, seeks group status for “all conservative and libertarian groups targeted for additional scrutiny” between March 2010 and May 2013. It’s also seeking unspecified monetary damages for the alleged violation of its constitutional rights and the costs associated with trying to comply with IRS demands.

The lawsuit is being backed by Citizens for Self-Governance, a group launched by Tea Party Patriots co-founder Mark Meckler.

Meckler claims that IRS agents also demanded massive amounts of disclosure of information not authorized by the Internal Revenue Code or any other federal law. The suit alleges that the tactic was used to delay or dissuade conservative groups from going through with their applications.

The IRS acknowledged that employees at its Cincinnati office had targeted conservative groups, creating massive amounts of paperwork or rejecting applications altogether.

Fox News' Chad Pergram and Fox Business Network's Rich Edson contributed to this report.