Blowout: On April 20, 2010, the Deepwater Horizon oil rig exploded, killing 11 people and spilling hundreds of thousands of barrels of oil into the Gulf of Mexico. The three companies involved—BP, Halliburton, and TransOcean—were named as codefendants in a federal lawsuit in September 2010.

The three have long pointed fingers at each other as being culpable for the explosion. In particular, BP blamed Halliburton for using shoddy concrete to seal the well in to place. In an internal report that is no longer available on the Internet, BP took full credit for only one of eight factors it determined caused the blowout. Both TransOcean and Halliburton responded indignantly to BP’s claims of their wrongdoing.

In November 2012, BP pleaded guilty to 14 criminal charges and will pay $4.5 billion in penalties. Earlier this year, TransOcean also pleaded guilty and agreed to pay more than $400 million.

Blowup: Although BP report obviously attempted to shift blame to its codefendants, it seems that they weren’t alone. On July 25, Halliburton pleaded guilty to one count of destroying evidence and agreed to pay the maximum penalty, according to a news release from the U.S. Department of Justice.

The evidence destroyed was related to Halliburton’s claim that BP significantly weakened the drilling structure by using only six centralizers to hold the drill pipe in the center of the well instead of the 21 Halliburton had suggested, according to the Washington Post. Later internal simulations by Halliburton that refuted that claim were destroyed while Halliburton continued to use the contention to cast dispersion on BP.

Blowback: Although the Justice Department has agreed not to file further criminal charges against the company in exchange for the plea, legal experts postulate that the admission will work against Halliburton in civil cases still to be decided, according to the *New York Times.

“This could impact how the civil litigation is resolved, potentially imposing more liability on Halliburton than we originally thought,” Carl Tobias, a law professor at the University of Richmond, told the Times.

The U.S. District Court for the Eastern District of Louisiana has created a Web site to help those interested follow the more than 200 cases related to the spill.