Countrywide Financial Corp. co-founder Angelo Mozilo hasn’t entirely escaped prosecutors’ wrath for his company’s risky lending. A U.S. government task force wielding an innovative legal strategy plans to bring a civil case against him over the excesses of the subprime-mortgage boom.

The last-ditch effort comes three years after the Justice Department abandoned a criminal probe of Mozilo. In 2012, public anger over the lack of prosecutions stemming from the financial crisis spurred the Obama administration to create a team devoted to investigating fraud in mortgage-backed securities. The group has wrestled at least $20 billion from Wall Street banks using a law with a relatively low threshold for suing and a long period to bring cases.