Investigators have pored over evidence for four years - a human tooth found at the bombing site, a suicide truck that was stolen in Japan and made its way to Lebanon, reams of phone records and hundreds of interviews. Now the focus in one of the Mideast's most dramatic political assassinations is shifting to prosecution, with the convening Sunday of an international tribunal on the slaying of former Lebanese Prime Minister Rafik Hariri. Despite the start of proceedings in the Netherlands, it is still not known who will be accused in the suicide truck bombing that killed Hariri and 22 other people on a seaside street in Beirut on Feb. 14, 2005. Also unknown is the most politically explosive question - whether the proceedings will implicate Syria's government, which many Lebanese believe was behind the murder of a man who broke with Syria and began to oppose its long military dominance of Lebanon months before his death. Syria has denied any involvement. Most likely the first defendants before the court will be four pro-Syria generals who led Lebanon's police, intelligence service and an elite army unit at the time of the assassination. They are the only people in custody, though they have not been formally charged. The current investigator who becomes the court's prosecutor as of Sunday, Daniel Bellemare of Canada, was quoted by the pan-Arab Al-Arabiya TV channel late Saturday as saying he will request the transfer of the officers to the custody of the court in the Netherlands. He did not give a time frame. But Robin Vincent, the tribunal's registrar, has said the prosecutor has 60 days from the formal opening on Sunday to request suspects be turned over for trial. Some in Lebanon doubt the court will ever bring out the full truth, believing it might avoid digging deep to ensure Syria does not react by stirring up trouble in Lebanon and other parts of the region. Trials could also further polarize Lebanon's politics, feeding the power struggle between pro- and anti-Syria factions. The UN Security Council had to impose the mixed Lebanese-international Special Tribunal after Lebanon's parliament was too divided to approve it. Edmond Saab, executive editor of the Lebanese newspaper An-Nahar, contends the tribunal will be immune from politicization. "Being an international court is a guarantee in itself against that, and the United Nations' credibility is on the line," he told The Associated Press. Administrators have said the tribunal will take up to five years to finish its work, and Bellemare said in a separate statement Saturday that it will be thorough. "We will not be deterred by the obstacles or the size of the challenges," Bellemare said. "We will go wherever the evidence leads us. We will leave no stone unturned." As prime minister, Hariri, a billionaire businessman, was credited with rebuilding downtown Beirut after the 1975-90 civil war, and with trying to limit Syria's influence. In a country known for political assassinations, his killing stands out for its far-reaching impact. It galvanized opposition to Syria and helped force the end of a 29-year military presence that dominated Lebanese affairs. But his death also threw Lebanon into turmoil. Anti-Syria factions supported by the West won control of the government but were unable to exert any authority while locked in a struggle with Syria's allies, led by the Hezbollah militant group. The first UN investigator into the killing, Detlev Mehlis of Germany, said the assassination plot's complexity suggested a role by the Syrian intelligence services and its pro-Syria Lebanese counterpart. Lebanon's pro-US government detained the four generals. But the two chief investigators who followed Mehlis have worked quietly and have not named any individuals or countries as suspects. Last April, Bellemare said investigators had evidence Hariri's killing was done by a "criminal network" also linked to a series of bombings and shootings that have killed seven anti-Syria figures and caused other deaths since Hariri's assassination. The UN team worked under tight security for fear of attacks or intimidation, living in fortified compounds in Beirut and traveling in heavily protected motorcades. The team also kept tight control of information about the investigation. One piece of evidence is the tooth of the suicide bomber. Forensic examinations determined the truck's driver was a man in his 20s who was not from Lebanon, according to Bellemare's predecessor as top investigator, Serge Brammertz of Belgium. Investigators interviewed hundreds of people, including the presidents of Lebanon and Syria. They acquired records listing more than 5 billion telephone calls and mobile phone text messages. They determined the truck used in the bombing was stolen in Kanagawa, Japan, in October 2004 and purchased two months later near the northern Lebanese city of Tripoli. The probe has also seen numerous twists. Husam Husam, a Syrian barber and self-proclaimed intelligence operative, at first implicated Syrian officials in testimony to investigators. Then he left Lebanon for Syria and appeared on TV, recanting and saying the Hariri family paid him to frame Syria. Lebanon's government dismissed the claim. Another purported Syrian intelligence officer, Mohammed Zuhair Siddiq, was at first said to be a key witness, then a suspect - then he vanished while under house arrest in France. A Lebanese man who was questioned about the sale of cell phone chips allegedly used for communicating in the bombing was found dead in what was ruled a car accident. Syria's interior minister, Brig. Gen. Ghazi Kenaan, died in his Damascus office in late 2005 about a month after speaking with investigators. Syrian officials said he shot himself to death, but some in Lebanon believe he was killed. Kenaan ran Lebanon for two decades until 2003.