"He may have convinced himself that he was in fear of his life, but whether or not he was is not definitive," Grenier said.
Zimmerman's responses would be more meaningful, he said, if he had been asked, " 'Did Trayvon Martin attack you and knock you to the ground?' Or 'Was Trayvon Martin on top of you hitting you before you shot him?' "
Joe Navarro, a former FBI agent who teaches interviewing techniques at Saint Leo University, agreed. "You have to ask precise questions," he said. "You want to know at what point you feared for your life."