Mahmoud Omar recorded hundreds of hours of conversations involving the suspects - five foreign-born Muslims who grew up in Cherry Hill.
The government sees those recordings as a key to the case: They contain talk of attacking Fort Dix or other U.S. military sites.
Defense lawyers have tried to damage Omar's credibility and show that their clients didn't plot anything.
After defense lawyers finishing cross-examining Omar on Tuesday, government prosecutors will be able to ask him further questions.
