Five Somali men accused of firing assault rifles at a Navy ship off the coast of Africa, are set to face the first U.S. piracy trial, in more than 100 years.

The suspected pirates are accused of shooting at the USS Nicholas in an attempt to plunder what they thought was a merchant ship. Instead, they fired on a battle-tested, 138-meter ship patrolling the pirate-infested waters, which shot back, forcing the men to flee in their small skiff, prosecutors said.

The men, along with other suspected pirates, were eventually captured and brought back to the U.S. to stand trial.

Yet, until now, no case has actually gone to a jury. The federal trial will begin Tuesday and is expected to last about a month.

The most infamous pirate captured in the spring was Abdiwali Abdiqadir Muse. The Somali suspect who staged a brazen high-seas attack on the U.S.-flagged Maersk Alabama, pleaded guilty in New York to charges, he hijacked the ship and kidnapped its captain. He faces a minimum of 27 years in prison.

The group of men accused in the USS Nicholas attack April 1 face a much stiffer punishment if convicted of piracy, which carries a mandatory life sentence. Yet the charge may be difficult to prove for prosecutors, in part because the suspected pirates never actually boarded the vessel.

The government acknowledges the five defendants did not take control of the Navy frigate with a crew of 100 highly trained sailors, which defence attorneys argue is necessary to prosecute the piracy count.

“They fired on a Navy ship. That’s the whole case,” said David Bouchard, an attorney for the Somali men. ” They didn’t go on the boat. They didn’t shoot anybody. They didn’t rob it.”

In a similar, but separate case involving a group of alleged pirates who are suspected of firing at the USS Ashland on April 10, a federal judge has thrown out the piracy charge, ruling there was not enough evidence to prove the charge.

Prosecutors are appealing the judge’s decision.

The USS Nicholas piracy trial would be the first in the US in at least a century, according to legal and maritime scholars. Other countries have recently held piracy trials, but one of the last in the U.S. was in 1861, when 13 Southern privateers aboard the Savannah were prosecuted in New York City. The jury deadlocked and the men were later exchanged with the South.

The defendants in the USS Nicholas case are also charged with plundering, firearms counts, assault and other charges.

These cases are part of a larger U.S. policy debate over how best to deal with the insurgents and criminals in Somalia, a poor and barely functioning nation that is suspected of harbouring al-Qaida-linked terrorists.

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