The assassination also inflamed political and sectarian tensions inside Lebanon and across the Middle East, particularly when investigators started probing potential Hezbollah links to the death of a politician who was backed by the West as well as Sunni Gulf Arab states opposed to Tehran.
Hezbollah, which is both a political party in Lebanon's government and a heavily armed guerrilla group, denies any role in Hariri's killing and dismisses the Netherlands-based tribunal as politicised.
Few expect the defendants to be handed over if convicted, but any guilty verdicts could pose a problem to the government and deepen rifts unresolved since the 1975-1990 civil war. The country is already reeling from the worst economic crisis in decades and a deepening COVID-19 outbreak.
Hezbollah has been designated a terrorist organisation by the United States, Canada, Germany, Britain, Argentina and Honduras as well as the Sunni Muslim Gulf Cooperation Council (GCC), which includes Saudi Arabia, the UAE, Bahrain and Kuwait. The EU classifies Hezbollah’s military wing as a terrorist group, but not its political wing.
Hariri's supporters, including his son Saad who subsequently also served as prime minister, say they are not seeking revenge or confrontation, but that the court verdict must be respected.
"We... look forward to August 7 being a day of truth and justice for Lebanon and a day of punishment for the criminals," Saad Hariri said last week.
Hariri stepped down as prime minister in October after failing to address demands of protesters demonstrating against years of corruption by a ruling elite which has driven Lebanon to its current financial crisis.
His successor Hassan Diab, backed by Hezbollah and its allies, says the country must avoid further turmoil over the tribunal verdicts. "Confronting strife is a priority," Diab tweeted last week.
In the Feb. 14, 2005 bombing, a truck laden with 3,000 kg of high-grade explosives blew up as Rafik Hariri's motorcade passed Beirut's waterfront Saint Georges hotel, killing him and 21 other people and leaving a huge crater in the road. urn:newsml:reuters.com:*:nL8N2F40HZ
Salim Jamil Ayyash, Hassan Habib Merhi, Assad Hassan Sabra and Hussein Hassan Oneissi are charged with conspiracy to commit a terrorist attack. Ayyash is charged with committing a terrorist act, homicide and attempted homicide.
Prosecutors said data culled from telephone networks showed that the defendants called each other from dozens of mobile phones to monitor Hariri in the months before the attack and to coordinate their movements on the day itself.
The men have not been seen in public for years.
Hezbollah has often questioned the tribunal's integrity and neutrality, saying its work had been tainted by false witnesses and reliance on telephone records that Israeli spies arrested in Lebanon could have manipulated.
"It is Hezbollah's right to have doubts about the court, which transformed into political score-settling far from the truth," said Salem Zahran, an analyst with links to Hezbollah leaders. Any verdict "has no value" to the group, he said.
Nabil Boumonsef, deputy editor-in-chief of Lebanon's An-Nahar newspaper, said neither Saad Hariri nor Hezbollah chief Sayyed Hassan Nasrallah wanted to escalate tensions.
But he expected Hariri to call for the defendants to be handed over if found guilty - which would leave Hezbollah on the defensive politically despite its military strength. If the group refused to surrender them it could put the government which it helped put together in difficulty.
As it tries to tackle the deep economic crisis, a guilty verdict could also jeopardise Lebanon's efforts, which have been supported by France, to win international aid.
"France... will have to take a position on Hezbollah after the verdict comes out on Aug. 7," Boumonsef said.
France hosted a donor meeting in Paris in 2018 when Beirut won more than $11 billion in pledges for infrastructure investment. Foreign Minister Jean-Yves Le Drian told Lebanese leaders in Beirut last month that Paris was ready to mobilise international support if Lebanon moved ahead with reform.
(Writing by Dominic Evans; editing by Philippa Fletcher) ((Dominic.J.Evans@Thomsonreuters.com, @DominicJEvans;))