“The government has no evidence that Izhar listened to the voice mail message,” the lawyer said. “The government is asking you to assume Izhar heard the voice mail.”

Then Rosenbaum told the jurors that they were the only thing “standing between the government steamrolling someone who is not guilty.”

But Shipley, the prosecutor, while acknowledging the son’s lesser role, sharply disagreed with his defense attorney.

“He undeniably knew of his father’s support,” Shipley said, “yet he agreed to help him anyway. That is a crime.”

Shipley, along with the first witness, FBI special agent Mike Ferlazzo, said the Khans’ alleged conspiracy to aid the Pakistani Taliban was sinister.

Ferlazzo said the Pakistani Taliban was founded in late 2007 as an “umbrella organization of different militant groups” that gained notoriety for murders, beheadings, kidnappings and improvised explosive devices.

The FBI agent noted the Taliban, now designated by the U.S. government as a terrorist organization, is linked to al-Qaida and has played roles in several attacks against Americans, including a December 2009 suicide bombing at a military base in Khost, Afghanistan, that killed seven U.S. citizens. The group also was connected to the attempt in May 2010 by Faisal Shahzad to detonate a bomb in New York’s Times Square.

Central to the prosecution’s case against the Khans are more than 1,000 phone calls and other communications intercepted by the FBI from 2009 to 2010. Based in large part on those calls, prosecutors say the Khans wired at least $50,000 to help finance the Pakistani Taliban’s acquisition of guns and ammunition.

In addition, Shipley, the prosecutor, said Hafiz Khan’s Swat Valley religious school, which he had founded in the 1970s, was used by the Taliban to train and indoctrinate children in fighting Americans. The madrassa was shut down in 2009 by the Pakistani army.

Court documents also show that the recorded conversations contained anti-American rhetoric and strong support for the Taliban, mainly on the part of the older Khan.

In July 2009, for example, the FBI said Khan “cursed the leaders and army of Pakistan, and called for the death of Pakistan’s president and for blood to be shed in violent revolution.”