David Coleman Headley, 52, formally admitted to 12 terror charges in March 2010 after prosecutors agreed not to seek the death penalty or to allow him to be extradited to India, Pakistan or Denmark to face related charges.
He is expected to be sentenced to life in prison with no chance of parole.
The Mumbai siege, which began on November 26, 2008 and lasted nearly three days, saw 166 people killed and was the deadliest militant onslaught on Indian soil since independence.
US came under fire in India for reaching the deal with Headley, but prosecutors said it was well worth it given the valuable intelligence he provided in order to save his own skin.
Headley also testified against his childhood friend, Pakistan-born Chicago businessman Tahawwur Hussain Rana, who was convicted on two terrorism charges last year.
Rana, 51, faces up to 30 years in jail for helping the banned Pakistan militant group Lashkar-e-Taiba (LeT) plan an attack on a Danish newspaper that sparked outrage by publishing cartoons of the Prophet Mohammed.
However, a jury found there was insufficient evidence that Rana was involved in the Mumbai attacks, even though Headley described how he had used Rana's immigration services business as a cover while conducting surveillance in India's financial capital.
Rana will be sentenced on January 15.
The only one of ten heavily-armed gunmen to have survived the three-day siege, Pakistani national Mohammed Ajmal Kasab, was hanged in an Indian prison last week.
(Read: Closure? Mumbai gunman Ajmal Kasab hanged)
COMMENTS (6)
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The Mumbai attackers in India and US have been senenced but here in Pakistan, the trial goes on endlessly, with no hope of a fair ending. No wonder we are at the bottom of all nations in terms of security.
@Raj - USA:
Terrorism of any form and in an country should be condemned. It is wrong and injustified. I'm glad that responsible people are being punished. But why only blame Pakistan for everything? Doesn't India participate in such activities? Directly or indirectly. The debate can go on forever. And you don't have to be sarcastic about 'practicing true islam'. It's always easy for people like you to comment without thinking whay they are talking about.
Sunny : Pakistan can never and will never learn. That country and that society is a sinking ship.
Pakistan too needs to move ahead with investigations in this case. Being in denial mode will be detrimental to it's own security. Religious radicalization can never be an asset.
"David Coleman Headley, 52, formally admitted to 12 terror charges in March 2010 after prosecutors agreed not to seek the death penalty or to allow him to be extradited to India, Pakistan or Denmark to face related charges."
Why he does not want to be extradited to Pakistan? He will be awarded the highest national honor and allowed to operate a charity and can live happily practicing true Islam.
However, he can be extradited to any country other than India, Pakistan or Denmark. He can be extradited to some other country that has lost its nationals. Sixteen countries other than India lost their citizens in these attacks.
Good Going!! Pakistan Govt should learn from india, how justice is served !!