A lawsuit that forced the Internal Revenue Service to publish a list of all groups that were potentially subjected to inappropriate scrutiny could lead to the deposition of Lois Lerner, former head of the IRS' tax-exempt wing and the unofficial face of the IRS scandal.

NorCal Tea Party Patriots, a California-based conservative group, filed the only successful lawsuit to date against the IRS for targeting practices that landed the agency in a firestorm of criticism in 2013. Last week, a judge in the Southern District of Ohio forced the IRS to release a list of 426 groups that may have faced discrimination when they applied for tax-exempt status.

Another IRS lawsuit, filed by the American Center for Law and Justice, was dismissed in District of Columbia court and is presently in the appeals stage.

Edward Greim, the attorney representing NorCal and the other groups represented in its class action suit, said the next step in the case involves reviewing documents and putting together a timeline of when the IRS singled out certain groups to receive intrusive questionnaires.

Among the list of potential IRS targets released last week were 12 groups whose titles include the word "occupy" and three that included the word "progress," suggesting left-leaning organizations may also have been subjected to inappropriate levels of scrutiny.

However, Greim said, their inclusion could indicate the IRS attempted to conceal its focus on conservative groups by padding its list of targets with liberal applicants once officials realized their actions were under investigation by a government watchdog.

"I think it would be circumstantial evidence that they knew their inspections were unauthorized," Griem said of the possibility that liberal organizations were thrown into the mix to dilute the scrutiny of Tea Party groups.

Mark Meckler, president of Citizens for Self-Governance, noted the latest list is larger than the one put forward three years ago by the Treasury inspector general for tax administration, which uncovered the targeting scheme in a May 2013 report. Meckler's group is financially backing the NorCal litigation.

"I think they realized they were in trouble because they had targeted only conservative groups," Meckler said, adding that attorneys on the case will now examine documents obtained through their litigation to determine whether progressive applicants were scrutinized before or after the inspector general began looking into Lerner's operation.

"The plaintiffs will request depositions of Lois Lerner and the seminal figures in the case," Meckler said. "The judge is required to allow us to depose all of these people; the question is, how much fight will the IRS put up?"

Meckler said the IRS has fought the conservative group at every stage of the case.

Lerner infamously invoked her Fifth Amendment rights and refused to answer questions when she was called before the House Oversight and Government Reform Committee to testify about the tax agency's targeting in 2013 and 2014.