The undercover agents were posing as members of al-Qaida, and supported the covert recordings by testifying that they hoped the suspect would walk away from the plot.
That narrative was challenged Thursday by celebratory debriefings -- meetings that were accidentally recorded -- in which undercover agents and their handlers said it was "fantastic" that Mohamed Mohamud asked them for explosives, a crucial step in the sting that culminated with Mohamud's arrest in November 2010.
"We are fortunate in this case that the government forgot to turn off its microphones," federal public defender Steve Wax said.
The inadvertent recordings could prove important to the defense's assertion that Mohamud was entrapped.
Wax said the attitudes that the FBI agents expressed in the recordings should be considered evidence that they were not merely assessing whether Mohamud was a threat, but rather were putting together a prosecutorial case before Mohamud did anything wrong.
"The government argues that they are imploring him not to do this," Wax said, "but when the agents are alone ... they're saying, 'Great, we're thrilled, good job.'"
Mohamud has been charged with attempting to blow up Portland's 2010 Christmas tree-lighting ceremony. The bomb was a fake provided by undercover FBI agents who met with their handlers after in-person conversations with Mohamud.
At least one of them left a recorder running, and among the agents recorded was "Hussein," the pseudonym of an undercover FBI agent posing as an al-Qaida bomb specialist who has testified over two days about his role in the sting.
Wax tried to get the recordings entered into evidence Thursday, but U.S. District Court Judge Garr King declined, saying Wax could play them only if he needed to rebut a statement from "Hussein."
That began an hours-long cat-and-mouse game, with Wax questioning "Hussein" on his intentions during the sting. The agent assented that he was happy Mohamud picked a "sexy" crime and thought the FBI had enough evidence in mid-November to make an arrest.
He didn't challenge Wax on his state of mind during the recordings, so the recordings weren't played.
"There was no sadness that a teenage American kid (met) with supposed al-Qaida figures in the way that Mohamud did?" Wax asked.
"No sadness," the agent responded.
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