Prosecutors have demanded life in prison for several officers in command at the time of the 2010 Israeli raid, but it appears unlikely that any sentence could be carried out.
The case symbolizes the rupture between Turkey and Israel, former allies whose diplomatic ties are effectively frozen. Israel has rebuffed Turkish demands to apologize for the raid on the ship and to compensate those killed as a precondition for normalizing relations.
Hundreds of people gathered outside an Istanbul criminal court that planned to hear testimony from passengers who were on the Gaza-bound ship at the time of the Israeli raid, as well as relatives of those who were killed. Nine pro-Palestinian activists—eight Turks and a Turkish-American—were killed aboard the vessel Mavi Marmara, part of an international flotilla trying to break the blockade, which Israel says it imposed in 2007 to keep Palestinian militants from bringing weapons into Gaza.
Turkey disputes Israeli assertions that its soldiers acted in self-defense after being attacked by activists when they boarded the ship. The commando operation sparked condemnation worldwide and led to an easing of Israel's blockade on the coastal territory.
The accused include Israel's former military chief, Lt. Gen. Gabi Ashkenazi, and three other former commanders.
"The trial will look into what the commanders did, what crimes were committed aboard the ship. There may also be additional indictments along the way," said Gulden Sonmez, a spokeswoman for IHH, an Islamic aid group that had operated the Mavi Marmara.
Sonmez said Israel would be required to give up the defendants if they are convicted, and that other countries would be required to do the same if they are caught elsewhere in the world. Israel scoffed at that assertion, describing the Turkish trial as a "kangaroo court" aimed at stoking anti-Israeli propaganda.
"The so-called accused were not even informed or served or notified that they were going to be charged, which makes this one big puppet show," said Yigal Palmor, spokesman for Israel's Foreign Ministry.
A United Nations report into the 2010 Israeli raid described the blockade of Gaza as legitimate. It said violent activists on board the Mavi Marmara had attacked raiding Israeli naval commandos, but also accused Israel of using disproportionate force against the activists.