With $1 billion at stake, two banks facing a government lawsuit over toxic mortgage bonds are pointing the finger all over the place:

Nomura Holdings Inc. and Royal Bank of Scotland Group fight against a billion-dollar U.S. government lawsuit over mortgage-backed securities is ending where it started: with the banks blaming the housing crash.

Nomura and RBS are focusing on the lead-up to the 2008 financial crisis in a bid to fend off claims they sold defective securities to Fannie Mae and Freddie Mac. The banks are the first to go to trial against the Federal Housing Finance Agency after 16 others settled out of court.

Nomura and RBS have more than $1 billion at stake in a case marked by a series of rulings that went against them. The courtroom colloquy included at least one contentious exchange with the judge, who will decide the trial without a jury.

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As reported earlier, Nomura Holdings and the Royal Bank of Scotland’s trial with the Federal Housing Finance Agency is the first out of 18 lawsuits to reach trial, and now that all sides have presented their closing arguments, it’s in the hands of U.S. District Judge Denise Cote to decide what to do.

The FHFA is suing various big financial firms for the alleged misselling of toxic mortgages to Fannie Mae and Freddie Mac during the housing boom. The FHFA says the mortgages defaulted in large numbers, requiring default on the Fannie and Freddie bonds and led the bailout and conservatorship of the government-sponsored entities.