Attorney General Eric Holder strongly condemned "stand your ground" laws Tuesday, saying the measures "senselessly expand the concept of self-defense" and may encourage "violent situations to escalate."

On the books in more than 30 states, the statutes have become a focal point of a complicated national debate over race, crime and culpability in the wake of the shooting of Trayvon Martin, an unarmed 17-year-old, by a neighborhood watch volunteer in Sanford, Florida. The volunteer, George Zimmerman, was acquitted of murder charges on Saturday.

Zimmerman did not cite Florida's "stand your ground" law — which says people who feel threatened can defend themselves with deadly force and are not legally required to flee — in his trial defense. Still, the instructions given to the jury said that as long as Zimmerman was not involved in an illegal activity and had a right to be where he was when the shooting occurred, "he had no duty to retreat and the right to stand his ground."