Prosecutors say a father lied to the FBI to try to protect his terrorist son during an investigation of a 2009 plot to attack New York City subways.
But lawyers for Mohammed Wali Zazi insist he was in the dark about his son's failed scheme.
A jury heard the two portrayals of Zazi on Monday at opening statements at his trial in Brooklyn.
Zazi's son, Najibullah, pleaded guilty to charges he received explosives training from al-Qaida in Pakistan. He also admitted he sought to conduct a suicide bomb attack on the subways with two friends until he learned the FBI was watching him and abandoned the plot.
Prosecutors say the elder Zazi lied and destroyed evidence of his son's homemade explosives. The 55-year-old defendant from Colorado denies the obstruction-of-justice charges.