A refugee from Uzbekistan conspired to support a terrorist group financially and planned to travel overseas to join them, U.S. prosecutors said Thursday, walking jurors through a trove of phone calls, emails and other online activity they said proves the man's desire to help the group.

The start of Jamshid Muhtorov's trial comes more than six years after his arrest at a Chicago airport. The case led to the U.S. Justice Department's first disclosure that it intended to use information obtained through one of the National Security Agency's warrantless surveillance programs.

Muhtorov challenged the constitutionality of the warrantless surveillance program but Judge John Kane ruled in 2015 that the program may have potential for abuse but did not violate his rights.

Muhtorov's attorney said during opening statements that the former human rights worker did email with people who claimed to belong to the Islamic Jihad Union, but said he was play-acting as a distraction from a sometimes difficult transition to America and never sent the organization money or intended to join them.

Prosecutor Greg Holloway peppered his opening statement with references to recordings of Muhtorov's phone calls and emails, telling jurors that they would hear of Muhtorov's desire to help the terror group and become a martyr in "the defendant's own words."

After coming to the Denver area in 2007 through a refugee resettlement program, prosecutors said he became "frustrated with life" and began emailing with the terror group through its website. By 2012, he told an FBI informant of plans to join the group and become a fighter, Holloway said.

"You will see increasing resentment," Holloway said. "You will see bitterness and anger."

Muhtorov was arrested while waiting to board a flight to Istanbul, and Holloway said agents found $2,800 in cash, two new iPhones and a new iPad in his luggage. In a recorded phone call days before the flight, Holloway said Muhtorov asked his daughter to "pray for your daddy to become a martyr."

Muhtorov did feel discouraged at times by life in the U.S., said his attorney, Kathryn Stimson. He worked at a processing plant, a casino and then as a truck driver after being a human rights worker in Uzbekistan. She said he believed he was free to read and talk about whatever he wished in his new home, she said.

He also believed that the Islamic Jihad Union's priority was deposing the dictator leading Uzbekistan, she said. Conversations about joining or somehow helping the group were a fantasy, a way to feel like the respected human rights workers he once was, she said.

"He talked and he talked and he talked," Stimson said. "And he never did anything."

Muhtorov's defense team also highlighted the use of surveillance devices, telling jurors that "bugs" were planted in his home, phone and truck without his knowledge. Stimson said FBI agents spent months following Muhtorov, listening to his conversations and monitoring his online activity but "got nothing."

They then turned to another man from Uzbekistan, who she said became an informant to avoid charges of tax fraud, marriage fraud and immigration fraud. The unnamed informant developed a relationship with Muhtorov, passing information to federal authorities about Muhotorov's claims that he was taking on a role in the terror group.

Stimson said there is no evidence that Muhtorov's claims to the informant were true.

Stimson said Muhtorov did purchase a one-way ticket to Turkey but planned to study Islam in Istanbul before meeting with human rights organizations, hoping to help his brother who was living in a nearby refugee camp. The money was intended for his brother, she said.