The nation's largest banks, facing a torrent of lawsuits over shoddy mortgage securities, are pushing to overturn a series of tough rulings in an important case, the New York Times DealBook blog reported yesterday. In a rare move, 15 banks—including Bank of America, Citigroup, JPMorgan Chase and UBS—filed a motion in Federal District Court in Manhattan on Tuesday to throw out a series of decisions by Judge Denise Cote, according to a copy of the court filing. In doing so, the financial institutions are aiming to broaden the amount of evidence they can gather in the hopes of quashing the lawsuit. In 2011, the Federal Housing Finance Agency, which oversees Fannie Mae and Freddie Mac, accused the banks of duping the housing giants into buying $200 billion of mortgage securities that ultimately imploded during the financial crisis. On Wall Street, the lawsuit is considered a critical litmus test for how successful the banks will be in stanching their losses from the mortgage litigation. In November, Judge Cote denied requests by the banks to toss out the lawsuit altogether.