BP said today it has agreed to plead guilty to felony charges related to the Deepwater Horizon oil rig disaster two years ago. The explosion killed 11 workers and caused the biggest oil spill in U.S. history. The oil company will shell out $1.3 billion in criminal fines, part of an overall settlement of $4.5 billion.

We all know what happens to humans who are criminals, but what about a company?

“There is nobody to kick or throw in prison when you’re talking about a corporation,” says David Skeel, a law professor at the University of Pennsylvania. Corporations have personalities and cultures just like people, and a criminal conviction sends a message.

“We’re saying that that corporation culture or corporate personality has acted in a way that we believe to be criminal,” Skeel says.

BP has agreed to plead guilty to 11 felony counts of misconduct and one of obstruction of Congress. Some convicted corporate felons have been banned from doing business with the federal government.

Criminal charges are about deterrence, says Blaine LeCesne, professor at Loyola Law School in New Orleans

“The most effective way to do that against a corporation of course is to hurt its bottom line is to pay a criminal penalty that is meaningful in financial terms,” he says.

The $4.5 billion is less than BP’s profits last quarter. However, pending civil cases could drain more than $20 billion from the company.

“The most important cases are yet to be resolved,” says Abrahm Lustgarten, who covers BP for the investigative news organization ProPublica.

And, prison isn’t out of the question.  The Justice Department has charged two BP employes with manslaughter and a third with obstruction of Congress.