The government's plea deal with a key player in the 2008 Mumbai terror attacks was the right move, even though David Headley's involvement was far greater than the man he testified against earlier this month, U.S. Attorney Patrick Fitzgerald said.

Information gleaned from Headley's interrogations with federal investigators provided a detailed insight into ways terrorist groups and the Pakistan's Inter Services Intelligence (ISI) agency ran their operations, Fitzgerald said in a telephone interview with the investigative journalism website ProPublica.

Headley also can be called upon to testify against other Mumbai plotters. He pleaded guilty last year to his role in plotting the Mumbai attacks and was the prosecution's star witness in the trial of Chicago businessman Tahawwur Rana. Headley scouted targets for the attacks in Mumbai. Last week, a jury acquitted Rana of involvement in that attack, but found him guilty on charges related to a separate plot to attack a Danish newspaper and for supporting for the Pakistan-based terror group Lashkar-e-Tayyiba (LeT).

Rana helped provide Headley with a cover for surveillance trips to target the Danish newspaper, Jyllands Posten. The newspaper's 2005 publication of cartoons depicting the prophet Mohammad had led to violent protests across the Muslim world.

Headley testified that members of Pakistan's powerful spy agency, the ISI, helped orchestrate and finance the two plots.

Defense attorney Charles Swift said that Rana was wrongly implicated by Headley, who Swift argued agreed to testify against Rana to avoid the death penalty. He thought it unlikely that other top-level terror suspects hiding in Pakistan will ever be brought to trial.

Swift was not surprised by the mixed verdict, ProPublica reported.

"From the beginning we feared the verdict could be a compromise," he said. "That's why we asked to separate the Mumbai charges from the Denmark charges. There is more evidence on the Denmark plot. He was found completely not guilty on Mumbai."

Fitzgerald rejected that claim saying, "The verdicts are hardly as inconsistent and as some have made them out to be."

"The jury could give Rana the benefit of a reasonable doubt as to how much he knew about the Mumbai attacks," Fitzgerald said. "But Rana played a more direct role in Denmark. … And there was more corroborating evidence beyond Headley, whose credibility was challenged by the defense. Jurors naturally look for intrinsic corroboration. They want to see something in black and white."