James Cromitie, on trial for allegedly trying to blow up two Riverdale synagogues, told an FBI informant he thought Jews looked at him like they wanted to kill him when he wore his jalabiya, a traditional Muslim robe.

When the informant asked if that made him angry, Mr. Cromitie replied, “It doesn’t make me angry … it just makes me want to jump up and kill one of them.”

That scene was on one of the first recordings the prosecution played for the jury on Monday, the fifth day of the trial for the four men allegedly involved in the plot.

As conversations between FBI snitch Shahed Hussain and Mr. Cromitie filled the courtroom, jurors flipped the pages of their transcripts in unison, reporters scribbled notes, family members and supporters of the defendants sat quietly or shook their heads. Mr. Cromitie stared straight ahead.

Of the four men on trial, Mr. Cromitie was the first to meet with Mr. Hussain. Mr. Hussain’s testimony is central to the prosecution’s case.

“I’m gonna do something,” Mr. Cromitie said, in a recording made in a Philadelphia hotel room where he and Mr. Hussain were attending a conference in November 2008. “You better believe it. With or without you, I’m gonna do something, anyway. You understand? I still have to make some type of, some noise. I have to make some type of noise.”

Mr. Cromitie, the alleged ringleader of a group accused of attempting to bomb the Riverdale Temple, the Riverdale Jewish Center and shoot down planes at Stewart Air National Guard Base showed no emotion as federal prosecutors introduced compelling video evidence.

On one tape, Mr. Cromitie told Mr. Hussain he was afraid of going to Afghanistan or any Arabic country because American soldiers would kill him “for fun.” He continued by saying American soldiers shoot at people because they see “something shiny” and then said, “How come you don’t shoot at the star? It’s shiny right?”

As the tape played, Onta Williams, the defendant seated behind Mr. Cromitie, turned to his defense attorney, Mark Gombiner, and the two smiled at each other. Mr. Gombiner shook his head.