George Zimmerman laughs in court

Circuit Judge Debra Nelson ruled George Zimmerman's criminal justice education is relevant to the shooting of 17-year-old Trayvon Martin, and allowed testimony on that subject. On Wednesday, during testimony from a former teacher, Zimmerman openly laughed in court.

U.S. Army Capt. Alexis Francisco Carter Jr. told the Florida court that Zimmerman had been “one of the better students” in a Criminal Litigation course he taught that included the state’s “stand your ground” self defense law.

Defense attorney Don West asked Carter, "You don’t have to wait until you’re almost dead until you can defend yourself?" Carter's reply, "No, I would advise you probably don’t do that," prompted several seconds of laughter from Zimmerman.

The exchange, and Zimmerman's fit of giggles, were captured in this video by Fox News, at around the 1:50 mark.

“On the issue of injuries, though, when you talk about that with the class and your understanding of the law is that the focused is what’s going on in the person’s mind, not whether they have actually been injured,” West argued. “It’s the fear of the injury, is it not?”

"It’s imminent injury," Carter explained. "Or imminent fear. So the fact alone that there isn’t an injury doesn’t necessarily mean that the person did not have a real apprehension of fear. The fact that there were injuries have a tendency to show or support that that person had a reasonable apprehension of fear."

Carter also explained that he covered "imperfect defense" with his class, which he described as meeting an aggressor with disproportionate force, ultimately becoming the aggressor oneself.

But ultimately, Carter testified that "things can change in a matter of moments."