The defendants admitted taking part in an authorised protest and being in possession of Molotov cocktails, the source said.
During the December 2012 demonstration in the Shiite village of Dia near Manama, policemen were attacked and one was wounded.
Dozens of Shiites have been tried over unrest following Arab Spring-inspired protests in mid-February 2011, during which demonstrators called for reforms in the Sunni-ruled kingdom.
The Shiite-led protests led to a nationwide crackdown a month later, backed by Saudi-led Gulf forces which rolled into Bahrain in support of the ruling Al-Khalifa family.
Last year, authorities increased the penalties for those convicted of violence, introducing the death penalty or life sentences in certain cases.
At least 89 people have been killed in Bahrain since the protests began, according to the International Federation for Human Rights.
