Nearly three years after a deepwater well rupture killed 11 people and leaked an estimated 4 million barrels of oil into the Gulf of Mexico, the civil trial for BP and the other companies involved has begun in New Orleans.

The trial opened with an attack on the poor safety standards that led to the sinking of the BP-leased Deepwater Horizon rig. U.S. prosecutors are determined to prove gross negligence caused the worst environmental disaster in U.S. history.

The case about the extent of damage and fault is being heard by a federal judge without a jury, but few observers expect it to be decided before an out-of-court settlement is reached.

BP has resolved thousands of lawsuits out of court, including a record $4.5 billion plea deal with the U.S. government in which the company pleaded guilty to criminal charges, and a $7.8 billion settlement with people and businesses affected by the spill.

The British energy giant spent more than $14 billion on response and cleanup and paid another $10 billion to other businesses, individuals and local governments.

After the April 2010 blow out, it took 87 days to cap the oil well and stop the leak that blackened beaches in five states and crippled the region's tourism and fishing industries.

The first phase of the trial will determine the cause and apportion fault for the disaster. The second phase, not expected to start for several months, will determine how much oil was spilled in order to calculate environmental fines. The third phase will deal with environmental and economic damages.