Datu Unsay Mayor Andal Ampatuan Jr. is pictured in his cell in Manila before a court appearance in January. STORY HIGHLIGHTS- A witness testifies that a politically powerful family plotted the killings
- Fifty-seven people were killed in an ambush
- A provincial mayor is accused of being a ringleader
- A backhoe was ordered to cover the bodies, the witness says
- Philippines
- Maguindanao
(CNN) -- A landmark murder trial started Wednesday morning in Manila in what are considered the worst politically motivated killings in recent Philippine history.
The case opened with testimony from a prosecution witness who said he attended two meetings in November 2009, during which a politically powerful family plotted the killings of dozens of people in a convoy.
Details of the plot included ordering a backhoe to bury the bodies, according to the witness, who was a personal aide to the family's patriarch.
There are 196 accused, about 500 witnesses and more than 11,000 murder charges involved in the case, which is expected to take years.
The former mayor of Maguindanao province, Andal Ampatuan Jr., is accused of being a ringleader in the November 2009 massacre in Maguindanao.
Andal Ampatuan Sr. -- the former provincial governor and the father of Ampatuan Jr. -- also has been charged in the killings.
The wife and sister of political candidate Ismael "Toto" Mangudadatu and 30 journalists were among the 57 victims.
Mangudadatu had sent his family members to file paperwork allowing him to run for governor of Maguindanao. Their convoy was ambushed, and their bodies were found in a mass grave.
Maguindanao is part of an autonomous region in predominantly Muslim Mindanao, which was set up in the 1990s to quell armed uprisings by people seeking an independent Muslim homeland in the predominantly Christian Asian nation.
Journalist Winona Cuevas contributed to this report.