Thirteen of the defendants are being tried in absentia in the court, in the city of Qatif, the Ahlul Bayt News Agency reported.
Waleed Abu al-Khair, a prominent Saudi human rights lawyer, was sentenced to three months in jail Tuesday.
He and the other activists were arrested in 2011 for signing a petition that called on Saudi rulers to grant the right to peaceful assembly. The petition criticized prison sentences imposed on activists and urged an end to police shootings of protesters.
Protests calling for the release of political prisoners and an end to discrimination against the Shiite minority began in February 2011. The demonstrations spread in November 2011 after security forces fired on demonstrators, killing five and injuring scores more.
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