MANILA - The alleged masterminds of the Philippines' worst political massacre will learn their fate Thursday when a Manila court issues its verdict, in a test of the justice system for a nation with a deep-seated culture of impunity.

A decade ago, 58 people, including 32 media workers, were slaughtered and dumped into roadside pits during an attack that was also one of the world's worst mass killings of journalists.

Amid international outrage, the slaughter cast a harsh spotlight on the Philippines' deep-seated problems of all-powerful political dynasties, easy access to guns and official impunity.

Victims' families have endured a trial of 101 defendants marred by allegations of bribery, defense delays, the murder of several witnesses and a fear that the still powerful accused could be acquitted.

A guilty verdict "will be a strong signal to human rights abusers that they can't always get away with murder," researcher Carlos Conde of New York-based Human Rights Watch told AFP.

"A not guilty verdict would be catastrophic for the cause of human rights and justice," he said, adding acquittal would signal to warlords "that it's business as usual, that they can continue using violence, intimidation and corruption to rule their communities".

Leaders of the powerful Ampatuan family, who ruled the impoverished southern province of Maguindanao, are charged with organizing the November 23, 2009 mass killing in a bid to quash an election challenge from a rival clan.

Lawyers representing many of the victims' families told AFP the 101 defendants, who have pleaded not guilty, face up to 30 years in prison without parole if convicted of even one of the 58 murders.

The brazen attack was carried out in broad daylight on a convoy carrying an Ampatuan family rival's wife, relatives, lawyers and the journalists, who were killed in a hail of gunfire.

The murders exposed how then president Gloria Arroyo had tolerated the Ampatuans' heavily-armed militia as a buffer against Muslim rebels in the south, home to the Catholic nation's large Islamic minority.

Even routine court cases can take years to make it through the Philippine justice system, which is notoriously overburdened, underfunded and vulnerable to pressure from the powerful.

This case is no exception, and victims families have long worried the Ampatuans, who continue to wield political power and influence, could avoid convictions. -AFP