Barring any last minute settlement, BP will be back in court today. This time it’ll be fighting tens of billions of dollars in civil claims related to the 2010 Gulf oil spill. And just like the oil spill clean up, the civil trial is expected to be long and complicated.

Edward Sherman, a law professor at Tulane University Law School, says, assuming neither side blinks, “the first phase alone will probably take three months.” And that’s just to figure out which companies get how much blame.

It could be a year (or years) before we all know how much BP is going to have to pay up and before all the plantiffs — the feds, the states, private businesses and individuals — get their money.

So why fight it out?

“From a fianancial standpoint, that might benefit BP if they fight this to a bitter end and reduce the settlement,” says Morningstar analyst Stephen Simko, “but at the same time that would obviously keep them in the news and the oil spill in the news for a long time to come.”   

And with a potential settlement, BP’s calcuation isn’t the only one. You’ve got a whole lot of people fighting over a whole lot of money.

It’s messy. Just like the oil spill.