The government is not pressing for Headley to serve the maximum, life sentence.
Headley's different colored eyes are a fitting symbol of the double-agent role he has played for years.
He worked as an operative for Pakistani extremists and as an FBI informant and government witness.
Headley will be sentenced on Thursday.
We know the value of his cooperation as federal prosecutors have just filed papers laying out how long the terrorist should spend behind bars.
The horrific attack has become known as "India's 9-11".
The chief scout who did reconnaissance on each location for Pakistani terrorists was Chicago resident Headley.
According to a sentencing memorandum filed late Tuesday by federal prosecutors in Chicago, "Headley played an essential role in the planning" and "contributed to the deaths of approximately 164 men, women, and children, and injuries to hundreds more."
Read the government's position paper on Headley sentencing here
There were six Americans killed in the November 2008 attacks.
For Headley, who was taken into custody by the FBI in Chicago in 2009, "there is little question that life imprisonment would be an appropriate punishment."
But from the moment of his arrest, Headley began cooperating, according to the government.
Investigators said he explained the attack plan and the inner workings of the organization behind it. He named names, dates and places; eventually resulting in the indictments of seven other terrorists, according to authorities.
Only one of the others, Chicago travel agent Tahawwur Rana, was arrested. Rana was sentenced to 14 years.
When Headley appears in court Thursday, prosecutors will cite a "fair and just balance between the despicable nature of his crimes and the significant value of his cooperation" and say they plan to ask for a 30 to 35 year sentence.
In Headley's plea agreement with the U.S. government, he was spared the death penalty and extradition to India. He is a widely known and hated criminal in India.
Even though he pleaded guilty, he does still have an attorney, who has filed a request for a more lenient sentence but it is under seal.
We won't know what they believe Headley is entitled to until Thursday's court hearing.
