The Russian authorities say the "Arctic Sea" was carrying timber from Finland to Algeria when it was hijacked off the Swedish coast by armed pirates, most of them ethnic Russian residents of Estonia. The Russian Navy claimed it freed the ship's crew after discovering the vessel off the west coast of Africa.
Prosecutors said the accused hijackers had threatened to use weapons against the crew and demanded a ransom of 1.5 million euros ($2.1 million). The defendants pleaded guilty, although five of the men dispute details of the allegations.
But many of the circumstances surrounding the case remain unclear, leading defendants' relatives to believe the alleged hijackers were set up.
Reports from Israel at the time said the "Arctic Sea" may have been first intercepted by the Mossad intelligence service, and that Israel had warned the Kremlin to stop its shipment of arms.
Critics of the Russian authorities' version question why seven Russian naval vessels, including two nuclear submarines, were used to track down a ship carrying only cheap lumber.
After their arrest, the alleged pirates said they'd been conducting environmental work on a small boat in the Baltic Sea when a storm blew them off course. They said they were rescued by the crew of the "Arctic Sea" and later set up as part of a cover-up.
But one of the defendants later testified the hijacking was masterminded by an Estonian businessman seeking to make headlines that would generate business for private security companies.
Three of the alleged hijackers agreed to earlier plea bargains in Moscow, where they were sentenced to between three and seven years in prison.