CHICAGO — An American who played a central role in the 2008 terrorist attack in Mumbai, India, that left more than 160 people dead should spend between 30 and 35 years in prison because of his cooperation with investigators, US prosecutors argued Tuesday in asking for a relatively lenient sentence. David Headley, 52, pleaded guilty to several charges that accused him of conducting scouting missions ahead of the three-day attack, which has been called India's 9/11. The charges carry a maximum sentence of life in prison. But in documents filed in US District Court in Chicago, federal prosecutors argued that Headley should be credited for “the significant value provided by his immediate and extensive cooperation” following his 2009 arrest. Headley provided “insight into the personnel, structure, methods, abilities and plans” of the Pakistani group that carried out the attack, Lashkar-e-Taiba, according to the filing. He also testified against Tahawwur Rana, a Chicago businessman eventually convicted of providing aid to the group and backing a failed plot to attack a Danish newspaper after it published controversial cartoons. “Obviously he is being rewarded for cooperating and testifying against Rana, and that's a good thing,” said attorney James Kreindler, who represents the families of some American victims of the Mumbai attack. “Given his age, 35 years may be pretty close to a life sentence.” Headley's attorney, John Theis, declined comment. The government's court filing outlined details of the Mumbai attack on Nov. 26, 2008, noting the “staggering” death toll included many children and acknowledging that “the far-reaching and devastating impact of those attacks may never subside.” Prosecutors recounted how Headley's meticulous reconnaissance, including his suggestion about precisely where the terrorists could make an amphibious landing in Mumbai, made the assault all the more deadly. But the court documents also highlight how Headley agreed to talk almost immediately after his arrest at O'Hare International Airport in Chicago, even after he was told his answers could lead to his conviction for crimes that call for the death penalty. Under his 2010 deal with prosecutors, Headley agreed to plead guilty and cooperate in exchange for a promise that he would not face the death penalty or be extradited to India. Tuesday's filing offers few specifics but says Headley helped shed light not only on Lashkar's structure and leadership, but also on other planned attacks and potential targets — including valuable information about Ilyas Kashmiri, Al-Qaeda's military operations chief in Pakistan who was reportedly killed in a US drone strike in June 2011 in Pakistan's South Waziristan tribal area. “Headley answered their questions without any restriction, and the government understands that the Indian government found the information to be useful,” the court filing states.—AP