Washington - A Libyan militant accused of leading the September 11, 2012 attack on an American diplomatic compound in Benghazi that left the US ambassador and three others dead goes on trial Monday.Ahmed Abu Khattala is charged with 18 counts of murder, supporting terrorists and related charges in the trial in the federal district court in Washington, three years after he was captured in a commando raid and sent by ship to the United States.Khattala, about 46, was the commander of an Islamist militia in Benghazi, Ansar al-Sharia, which undertook the deadly raid on the US compound in the eastern port city.According to the indictment, he led a group of about 20 militants storming the compound. They set buildings on fire, including one that contained ambassador Christopher Stevens and a foreign service officers, killing them. Shortly afterward they killed two US security contractors in an attack on a CIA outpost near the mission compound.The attack shocked Americans but turned into a bitter political fight in which Republicans sought in a multi-year investigation to pin the blame for the popular diplomat's death on then-Secretary of State Hillary Clinton ahead of her planned run for the presidency. 13 days on a ship The trial of Khattala, who has pleaded not guilty, was stalled by a steady stream of motions challenging the way he was brought to the United States and the use of evidence from two interrogations.After his capture he was not spirited quickly back to the United States by jet, but placed on a navy ship for two weeks.There he first underwent five days of interrogation by intelligence agents.Then he was interrogated by a team from the Federal Bureau of Investigation for several days.In August the Washington court ruled against his lawyers' motion to suppress whatever he told his interrogators as evidence, because his rights to remain silent, know the charges against him and have a lawyer present were violated.His lawyers also argued that the lengthy 13 day trip by ship back to the United States was part of a scheme to extract information from him without legal protections.But in his August 16 ruling, Judge Christopher Cooper ruled that in fact FBI agents had repeatedly advised Khattala of his "Miranda" rights to have a lawyer present and to remain silent, and had "knowingly and intelligently" waived them."Abu Khattala was treated humanely and courteously: He was given breaks every hour or two, and offered snacks and refreshments," the judge said."The sheer number of times Abu Khattala waived his Miranda rights -- once in writing and twice verbally on each typical interview day -- is further evidence of the waivers' voluntariness."