Former IRS official Lois Lerner will testify before Congress Wednesday about the IRS scandal.

Lerner had refused to testify in May 2013. Rep. Darrell Issa said she will not get immunity for her testimony.

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The inspector general found that the IRS had pulled 298 applications for review and that the agency reviewed 100 percent of groups with the words “tea party” or “patriot” in their name. The IRS only reviewed 30 percent of groups that had the words “progressive” or “progress” in their name.

“It’s going to be a good, fact-finding hearing,” Rep. Darrell Issa (R-Calif.) said on “Fox News Sunday.”

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Issa, who is chairman of the House Committee on Oversight and Government Reform, said that officials know what Lerner did but not why she did it.

Congressional investigators want to know who told IRS agents to target the groups. However, Issa said that Lerner was “in a powerful position and could have been acting alone.”

Watch Issa's full interview above.