An American has been sentenced to 35 years in prison for helping plan the 2008 attack on Mumbai which left at least 166 people dead.
David Coleman Headley, 52, pleaded guilty in the case and co-operated to avoid the death penalty and extradition to India.
Prosecutors in Chicago had pressed for leniency as credit for Headley's co-operation with investigators, such as sharing intelligence about networks, including the Pakistani-based group that mounted the attack.
Rewarding Headley with the hope of at least a few years of freedom, they said, would encourage future suspects to talk.
Judge Harry Leinenweber said the Mumbai assault was so unfathomable and terrifying that "perhaps the lucky ones were the ones who didn't survive".
"I don't have any faith in Mr Headley when he says he's a changed person and believes in the American way of life," he said.
Headley's meticulous scouting missions helped facilitate the operation by 10 gunmen from Lashkar-e-Taiba.
Many of the victims of the attack said they were disturbed and upset that Headley did not get the maximum life sentence he faced.
Headly showed no emotion when the sentence was announced.
Hatred of India
The attackers arrived by boat on November 26, 2008, carrying grenades and automatic weapons, and fanned out to hit multiple targets, including a crowded train station, a Jewish centre and the landmark Taj Mahal Hotel.
Television cameras captured much of the three-day rampage live.
The attack had heightened the strain in a historically antagonistic relationship between India and Pakistan, which have fought three major wars.
Indian officials accuse Pakistani intelligence of helping to plan the assault - an allegation Pakistan denies.
Prosecutors said Headley, who was born in the US to a Pakistani father and American mother, was motivated in part by a hatred of India going back to his childhood.
Headley changed his birth name from Daood Gilani in 2006 so he could travel to, and from, India more easily to do reconnaissance without raising suspicions, videotaping and mapping targets for the gunmen.
The 12 counts Headley pleaded guilty to included conspiracy to commit murder in India and aiding and abetting in the murder of six Americans.
Prosecutors praised Headley for testifying against Tahawwur Rana, the Chicago businessman convicted of providing aid to Lashkar-e-Taiba and backing a failed plot to attack a Danish newspaper for publishing depictions of the Prophet Muhammad.
Rana, sentenced last week to 14 years in prison, claimed his friend Headley had duped him.
Late last year, India secretly hanged the lone gunman who survived the Mumbai attack, Mohammed Ajmal Kasab.