The protesters carried mock coffins to represent the victims, including 32 media workers, of the Nov. 23, 2009, massacre as well as dozens of other journalists killed in the Philippines since 1986.
Harry Roque, a lawyer for the victims, said he is pushing to shift the focus of the trial to members of a powerful political clan that allegedly masterminded the massacre instead of waiting for the presentation of the evidence for multiple murders against all of the accused.
Only 103 of 196 accused are in custody, including clan patriarch and former Maguindanao provincial Gov. Andal Ampatuan Sr., who allegedly masterminded the massacre, his son, Andal Jr. who witnesses say was among the gunmen, and several other sons and relatives. They have denied the murder charges.
The wife and female relatives, lawyers and supporters of Ampatuan's political rival, Esmael Mangudadatu, were en route to file his candidacy in provincial elections when gunmen allegedly led by Andal Jr. stopped them and led them to a hilltop clearing where they were mowed down and hastily buried in mass graves.
All 32 media workers who were in their convoy were gunned down, making it the worst killing of journalists in the world.
"You can never finish everyone at the same time, and you can never wait until everyone is finished before you come up with a judgment ... because there are so many victims, so many accused," Roque told The Associated Press in explaining why he wants verdicts against the political clan members first.
He cited the Nuremberg Trial after World War II where only about two dozen were tried despite the millions who were killed.
He proposed reducing the number of the accused "to those who took part in the shooting, those who took part in the planning." As an example, he said firing police officers who did not prevent the killings would be "punishment enough."
Since the trial began in January 2010, more than 260 twice-weekly hearings have been held and only 81 people have been arraigned. One of the principal accused, former regional Gov. Zaldy Ampatuan, another son of the clan patriarch, has not yet been arraigned.
Justice Secretary Leila de Lima said the defense was delaying the trial by filing motions questioning the presentation of evidence and witnesses. In all, 110 witnesses have testified. Prosecutors say at least six witnesses, potential witnesses and their relatives have been killed since the trial started in an attempt to suppress testimony.
The Center for Media Freedom and Responsibility, a media watchdog, said the trial needs to end in justice for the victims or "encouraged by the glacial pace of the trial and uncertainty of the culprits ever being punished, the killers of journalists and political activists will continue to kill with impunity."
The U.S.-based Human Rights Watch has criticized President Benigno Aquino III for not dismantling militias and private armed groups such as those utilized by the Ampatuans.
"Three years since the horrors of the Maguindanao Massacre, the trial crawls along, half of the suspects remain at large, and the victims' families still face threats," said Brad Adams, Asia director at Human Rights Watch. "Yet the larger problem is that the Aquino administration has done next to nothing to disband the rest of the country's private armies."
Presidential spokesman Edwin Lacierda said the Aquino administration, which took office in 2010, has urged the judiciary to "expedite the process without, of course, sacrificing due process."