Trial has yet to produce a single conviction, families are living in fear, and country's journalists remain vulnerable to attack

It was one of the bloodiest incidents in the Philippines' recent history, and the largest mass murder of journalists anywhere in the world. Fifty-seven people were killed when an eight-vehicle convoy carrying journalists, family members and supporters of a Filipino politician was ambushed on a stretch of rural highway in southern Maguindanao on 23 November 2009.

Men with automatic rifles and machetes shot, raped and beheaded many of the passengers, before dumping them and the vehicles in vast mass graves. Three years later, the victims' families are still waiting for justice.

Nearly 200 people – among them soldiers, police, civilian militiamen and prominent local politicians – have been charged with murder. But the trial, which since 2010 has been bogged down by bail proceedings, has yet to produce a single conviction.

The ambush was an attempt to derail the candidacy of Esmael Mangudadatu, a local mayor who was running for governor against a member of the powerful Ampatuan clan. Mangudadatu, sensing danger, was not part of the convoy, but 31 journalists were – making the ambush the most deadly single attack on the press ever, according to the International Crisis Group.

Several witnesses have been killed, and nearly half of those charged with murder are still on the run. Police suspect some of them may have sought refuge with the Islamist rebels of the Moro Islamic Liberation Front. It is no surprise that many of the victims' families still live in fear.

Some, like Grace Morales, whose husband and sister were among those killed, have reported repeated visits to their homes by unidentified men. Even Mangudadatu, now governor, who lost his wife and two sisters in the ambush, closely watches his security and recently said he was unable to attend scheduled memorial services this Friday because of safety concerns.

Despite widespread outrage about the massacre, the Ampatuans still enjoy high positions of power. According to Maguindanao: The Quest for Justice, a documentary about the massacre made by the Philippine Centre for Investigative Journalism, of the 10 Ampatuans linked to the ambush who ran in elections just one year later, eight won – five after campaigning while in hiding and another three while in jail.

The Ampatuans have seemingly wielded their power in other ways too. Last week the supreme court reversed its decision to allow live media coverage of the trial, meaning victims' families – many too poor to attend court proceedings in Manila – will not be able to watch the case.

According to family testimony, it also appears that emissaries acting on behalf of the Ampatuan clan have offered settlements of 25m pesos (£381,500), a huge sum in a region where 40% of the population lives on a dollar a day.

To date, however, all of the families have turned the money down, according to Morales, who heads the lobbying group Justice Now. "Many of [us] find it difficult to sustain any kind of livelihood, [as] most of those who died were breadwinners … [But] we want justice for the massacre and I think [that] is more important than the amount," she said.

The Philippines is an exceptionally media-rich country, boasting 500 newspapers and 650 broadcast stations, but Melinda Quintos de Jesus, of the Manila-based Center for Media Freedom and Responsibility (CMFR), said the country's journalists were "stunningly vulnerable" to attack and threat.

The weak rule of law, poor forensic capacity, limited protection system and prevailing culture of violence means that political warlords like the Ampatuans, local government officials who dislike criticism, and businessmen using guns for hire seemingly rule with impunity.

"Many cases don't ever get to court and the killers go unpunished and unapprehended, yet this is one of the strongest and oldest democratic countries in south-east Asia," Quintos de Jesus said.

According to CMFR figures, 128 Filipino journalists have been killed since 1986, most of them under the Gloria Macapagal-Arroyo administration, with only 10 convictions in that time. A further 21 have been killed since Benigno Aquino assumed power in February 2011, the most recent a radio reporter in September.

The high number of killings makes the Philippines the third most dangerous country in the world for journalists, behind Iraq and Somalia. Quintos de Jesus said journalists did not take the kind of precautions they should, and most treated death threats "like having a kind of Purple Heart".