Headley will testify in any future prosecutions of fugitive masterminds such as al-Qaeda chief Ilyas Kashmiri and LeT's Sajid Mir, who is charged with a lead role in the Mumbai plot, Propublica.Com quoted US Attorney Patrick Fitzgerald as saying.
Headley, a Pakistani-American, was the star witness in the recently concluded trial if Tahawwur Husain Rana, who was convicted by a Chicago court on two counts of terrorism related charges participating in the conspiracy of terror attacks in Denmark and providing material support to Lashkar-e-Taiba.
Rana, 50, however, was found not guilty on charges related to the Mumbai terrorist attacks. He now faces a maximum jail sentence up to 30 years.
"Fitzgerald declined to discuss details of the case such as the politically sensitive decision to indict a suspected ISI officer who served as Headley''s handler and is known only as Major Iqbal," ProPublica said.
At a news conference in Chicago last week, Fitzgerald vowed to bring the other six Pak-based defendants to justice who have been named in the indictment filed by federal prosecutors before the court.
Illyas Kashmiri, the Al Qaeda leader; Sajid Mir, the Lashkar-e-Taiba commander; Major Iqbal, said to be a serving officer of Pakistan's Inter Services Intelligence (ISI) and Abdur Rehman Hashim Syed aka Pasha, another LeT leader; are charged to be involved in the 26/11 attack, besides plotting a major terrorist attack in Denmark.
"We are hoping to see them brought to justice. We have to take that one step at a time," US Attorney, Patrick Fitzgerald had said.
Rana is the second defendant to be convicted among a total of eight co-defendants who have been indicted in this case since late 2009.
Co-defendant Headley, 50, pleaded guilty in March 2010 to all 12 counts against him, including aiding and abetting the murders of the six American victims.
Headley, who is facing a maximum sentence of life in prison, has cooperated with the government since he was arrested in October 2009, and testified as a government witness at Rana''s trial.
The six remaining defendants are believed to be hiding in Pakistan. It is understood that the United States is seeking extradition of all the six accused in the Chicago case.
Recent reports from Pakistan said that Kashmiri has been killed in a US drone attack, but the United States has not confirmed it.
"I am not in charge of drone attacks. I do not know what happened. We read news paper report.. I am not there, I do not know whether there was drone, what happened with the drone, is he alive or dead I can't say," the US Attorney said.