An American citizen who admitted to his role in laying the groundwork for the 2008 terror attacks in Mumbai, India was sentenced to 35 years in prison in a US federal court on Thursday.

David Coleman Headley, a US citizen of Pakistani heritage, pleaded guilty in 2010 to 12 charges related to the Mumbai terror attacks and a second plot to attack a Danish newspaper that sparked outrage over its publication of cartoons of the Prophet Mohammed.

Prosecutors did not seek the death penalty for Headley because of his cooperation with US investigators and intelligence officials upon his arrest in 2009. Headley admitted he had helped with identifying targets and a water-landing site for the attackers.

He also told prosecutors everything he knew from the seven years of working with Pakistani militants and the link between the terror operation in India and Pakistan’s intelligence service, the ISI, AFP reports.

“There is little question that life imprisonment would be an appropriate punishment for Headley’s incredibly serious crimes,” prosecutors said in their sentencing memorandum, but added that his extensive cooperation had been of “significant value” to US anti-terror efforts.

Former US attorney Patrick Fitzgerald said the information Headley provided “saved lives”.

US District Judge Harry D. Leinweber called Headley a “terrorist” and said he would rather impose the death penalty as he handed down the 35-year prison sentence.

“I’m hopeful it will keep Mr. Headley under lock and key for the rest of his natural life,” Leinweber said.

The Mumbai terror attacks left more than 160 people dead and hundreds wounded. Among those killed were six Americans.