If BP didn't realize it before, the US Supreme Court just made it unmistakably clear: The British oil producer has backed itself into a dangerously vulnerable position in the Gulf of Mexico spill-liability wars. The high court on Monday turned down BP's plea for an intervention in the multibillion-dollar litigation fracas stemming from the Apr 2010 disaster that killed 11 offshore rig workers and spewed millions of gallons of crude in the waters off Louisiana. In the narrowest sense, the Supreme Court's unwillingness to wade into the spill litigation means that an open-ended settlement of one portion of BP's liability will now cost billions of dollars more than the original $7.8 billion estimate. The company now estimates that its liability under the business-claims settlement will exceed $9.7 billion, and plaintiffs' attorneys newly encouraged to take a shot are predicting the figure will be much higher.