50-year-old Headley, a Pakistani-American, has been cross-examined by defence lawyers of Rana, a 26/11 co-accused and a Canadian of Pakistani-origin who is standing trial at a Chicago court here after being slapped with a dozen charges in connection with the Mumbai attacks in which 166 persons were killed.
Headley, who pleaded guilty to avoid the death penalty and extradition, wrapped up testimony with prosecutors saying they expect to call up to eight more witnesses starting today.
The FBI agents and Rana's relatives will be the next witnesses in the trial.
The defence lawyers said Headley lived multiple lives and used his friend over the years. Rana and Headley, who are both 50, met as teenagers at a Pakistani military school. Headley conceded that he was secretly researching on Internet at Rana's house.
"As expected this guy has a very troubled history and past," Patrick Blegen, Rana's attorney told reporters here after the trial at the Dirksen Federal Courthouse.
"It's my sense that he answered the questions affirmatively because we had a stack of papers to contradict him.
"He lied before in the past," Blegen said.
"Headley used Dr Rana from an early age and he's a criminal. He had no friends. He had only himself," Charlie Swift, another lawyer of Rana, said.
Swift said that Headley duped even his wives.
"Over the three days, he couldn''t hide the truth. Headley is a spider who spins the web so that everything works his way," Swift added.
"The true image of David Headley emerged over the last three days," Swift said.
During his testimony, Headley expressed remorse at the killing of Indian people at the trial.
"You are remorseful for what you have done?", asked Patrick Blegen, Rana's attorney to Headley.
"Yes, I feel bad about my grievances and the way I went to address them," Headley said.
Earlier Headley had told the FBI that the attacks according to him were a "justifiable revenge".
"You've been converted from your previous ways?", Blegen asked.
"Yes," Headley replied.
"When did you have the conversion?," Blegen asked.
"I don't have an exact date but I'm still in the process," Headley said.
But, Blegen said, "I don't think he had any remorse." Swift said that Headley gave Rana money to keep Rana in his traps."
"Headley has always manipulated people- always does. He did it for years before he made friends with Rana not for today but for years," Swift said.