The hearing is being guarded with extra security, with personnel from the police and the military seen ready with a water cannon and antiriot vehicles in the court parking lot, kompas.com reported Thursday prior to the hearing.
Security screening has also been tightened for people wanting to enter the court.
Ambulances were also seen near the court building.
In February, about 1,500 people attacked members of the Ahmadiyah sect in Cikeusik, Banten, killing three.
Eleven defendants are being jointly tried for an assault causing death, inciting violence, mistreating others, participating in an assault and illegally possessing sharp weapons.
However, prosecutors have declined to charge anyone with the murder or manslaughter of the three Ahmadis.
Legal activists monitoring the trial including from the Institute for Policy Research and Advocacy (Elsam) previously said the prosecutor involved in the case had show a substandard performance. (rpt)