CHICAGO - Defense attorneys on Wednesday scrutinized the relationship between an admitted American terrorist and the Chicago businessman accused of helping him scout sites for the deadly 2008 Mumbai attacks, working to persuade jurors that their client had merely been manipulated by a trusted friend.

David Coleman Headley, a former Philadelphian, pleaded guilty last year for his role in the three-day siege in the Indian city, which killed 164 people. To avoid the death penalty, he agreed to testify against his longtime friend Tahawwur Rana, who is accused of providing cover for Headley's surveillance.

Rana's attorneys wasted no time painting their client as a good guy with the wrong friend, setting up a main theme for the defense.

"He was your friend, but he didn't do what you were doing?" asked Rana defense attorney Charles Swift.

"Yes," Headley answered.

Headley, who was born in the United States to a Main Line socialite but spent much of his life in Pakistan, is the government's top witness in a trial that comes at a fragile time in U.S.-Pakistan relations. His testimony has so far detailed how Lashkar-e-Taiba, a Pakistani extremist group blamed in the attacks, and Pakistani intelligence coordinated in plotting and funding the attacks. The trial also comes just weeks after Osama bin Laden was found hiding outside Islamabad, raising concerns that Pakistan may have been protecting him.

Rana and Headley, both 50, met years ago at a prestigious boarding school in Pakistan. But Headley detailed their different experiences under defense questioning.

Headley described Rana as a top student who attended medical school and adhered to strict religious beliefs, including no alcohol or dating. Headley, meanwhile, said he used and smuggled drugs and dated multiple women.

When asked to describe himself as a student, he simply said: "Very bad."

He told attorneys he had tried to persuade Rana to join Lashkar. But Rana declined because he said he didn't espouse the group's beliefs.

Headley has testified that Lashkar and Pakistan's Inter-Services Intelligence agency operate under the same umbrella. Pakistan denies any links.