The 90-page complaint contains lots of detail about the role that BofA's lawyers at Wachtell, Lipton, Rosen & Katz played during the turbulent deal to acquire Merrill Lynch. The AG owes a big thank you to Wachtell litigation partner Eric Roth, who took copious notes that the AG repeatedly cites as evidence.

In the wake of the financial crisis, Moody's, Fitch, and S&P have managed to handily defeat nearly all investor claims over AAA rated securities-gone-bad. But it's a different story if investors have evidence that the ratings agencies collaborated with banks to create risky financial products and tailored their ratings to seduce investors.

For Martens and his bosses in Washington, the stakes in the trial of Fabrice Tourre were huge.

Despite some recent defense setbacks, the credit ratings agencies are still proving to be tough litigation targets for investors that placed losing bets on mortgage-backed securities.