The important passages, she said, were those where Mr. Naseer went into detail about women and cars — a car bomb was one of the methods he was considering, she said.

For instance, Mr. Naseer wrote once that a woman named Huma seemed “weak and difficult to convince.” That, Ms. Ahmad argued, referred to a hydrogen peroxide bomb, which requires a long time to become concentrated enough to work, though the prosecutor did not point to evidence in the trial backing up that point.

“Think about what good code it is: two guys speaking about cars and girls,” she said.

She also highlighted apparent inconsistencies in Mr. Naseer’s argument. In Mr. Naseer’s final email to the sana_pakhtana address, days before he was arrested in England, he refers to his wedding later in the month.

Mr. Naseer had broken up with his girlfriend by that point and was not speaking to her, Ms. Ahmad said, making it hard to believe that he was planning to marry her. In the email, he also says he wishes sana_pakhtana could be at the wedding. Either “the defendant wants his random Internet friend to come to his wedding,” Ms. Ahmad said, or he is alerting his Qaeda handler that an attack is ready.

Mr. Naseer is representing himself, and much of his summation was tedious; he spent more than two hours reading transcripts aloud.

However, when he broke from that, he was engaging, making eye contact with jurors as he read from a white legal pad as he said that the government had not proved its case.

“Did anyone say anything about the defendant’s extremist views?” he said. “Did anyone give evidence to the fact that Abid Naseer and his friends were preparing explosive material?”