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FILE - The Deepwater Horizon oil rig burns in the Gulf of Mexico, more than 50 miles southeast of Venice on Louisiana's tip, in this April 21, 2010 file photo. A high-stakes trial to assign blame and help figure out exactly how much more BP and other companies should pay for the spill began Monday, Feb. 25, 2013.
A high-stakes trial started Monday to assign blame and help figure out exactly how much more BP and other companies should pay for the 2010 Gulf oil spill. Under the Clean Water Act, which is designed to punish companies and prevent future spills, a polluter pays a minimum of $1,100 per barrel of spilled oil; the fines nearly quadruple for companies found guilty of grossly negligent behavior.

Here's a gallery of photos looking back at the aftermath of the nation's worst offshore oil spill.

FILE - United States Fish and Wildlife biologist Kayla Dibenedetto attempts to catch an oiled Brown Pelican at Grand Isle, La., in this June 5, 2010 file
FILE - United States Fish and Wildlife biologist Kayla Dibenedetto attempts to catch an oiled Brown Pelican at Grand Isle, La., in this June 5, 2010 file photo. Oil from the Deepwater Horizon has affected wildlife throughout the Gulf of Mexico. A high-stakes trial to assign blame and help figure out exactly how much more BP and other companies should pay for the spill began Monday, Feb. 25, 2013. ((AP Photo/Charlie Riedel, File))


FILE - Crude oil from the Deepwater Horizon oil spill washes ashore in Orange Beach, Ala., in this June 12, 2010 file photo.  Large amounts of the oil
FILE - Crude oil from the Deepwater Horizon oil spill washes ashore in Orange Beach, Ala., in this June 12, 2010 file photo. Large amounts of the oil battered the Alabama coast, leaving deposits of the slick mess some 4-6 inches thick on the beach in some parts. A high-stakes trial to assign blame and help figure out exactly how much more BP and other companies should pay for the spill began Monday, Feb. 25, 2013. ((AP Photo/Dave Martin, File))

FILE - A small dead fish floats on a pool of oil at Bay Long, off the coast of Louisiana, in this June 6, 2010 file photo. Oil from the Deepwater Horizon
FILE - A small dead fish floats on a pool of oil at Bay Long, off the coast of Louisiana, in this June 6, 2010 file photo. Oil from the Deepwater Horizon has affected wildlife throughout the Gulf of Mexico. A high-stakes trial to assign blame and help figure out exactly how much more BP and other companies should pay for the spill began Monday, Feb. 25, 2013. ((AP Photo/Charlie Riedel, File))