Horn turned down an ABC News request for an interview but his attorney Tom Lambright insists Horn was entirely justified.
"He was afraid for his life," Lambright said. "He was afraid for his safety, and then they charged him. I don't think Joe had time to make a conscious decision. I think he only had time to react to what was going on. Short answer is, he was defending his life. "
Lambright acknowledged that the 911 dispatcher urged Horn to stay inside but said, "Joe was doing what he thought was necessary. As a man, he thought it was his duty to protect his house, his neighborhood, his community."
The Horn case has aroused plenty of passion. At a recent demonstration outside his home, police in riot gear stood by as activists demanded prosecution while counter-demonstrators defended him, including a group of bikers led by Randy Laird.
"In this grand jury decision, we look for a complete acquittal, no charge of any kind, and that's what we believe will be right," Laird said then. "That's what's going to make either the Castle Doctrine stand or fall."
The Castle Next Door Some prosecutors are wary of "Castle Law."
"There's too many imponderables in this law, whereas the previous law was working just fine," said Warren Diepraam, the Harris County Assistant District Attorney. "Frankly, life is precious."
The critical legal question hinged on whether Horn acted in a reasonable way to defend his neighbor's property.
"You cannot take another person's life in defense of their property unless you're somehow given permission by the other person to protect their property," Diepraam said.
On that 911 call, the dispatcher asked Horn directly about the owners of the house that was being burglarized, and whether he knew them.
"I really don't know these neighbors," Horn said. "I know the neighbors on the other side really well & I can assure you if it had been their house, I'd already have done something." Still, Lambright says that his client "absolutely" had his neighbors' permission.
"There's no question about it," he said. "They'd tell you today that they are very happy that he was there and that he was watching out. Every neighbor in the state of Texas watches out for one another."
"In most situations, calling 911 is the best remedy, not calling out for your 9-millimeter," Diepraam said.
'A No-Brainer' Damon Barone, who killed a burglar in his own home, isn't sure whether Joe Horn was justified, but he does believe the Castle Doctrine has already delivered a crystal clear message to criminals.
Barone said that in Texas, the occupational hazard of burglarizing someone's home is "death."
"If you're lucky, you'll get arrested and sent to jail," he said.
In December 2007, Barone confronted a burglar breaking into his Houston home in the middle of the night. His wife, baby daughter and 6-year-old son were asleep when Barone heard a commotion and grabbed his Glock handgun.
"I heard a crashing through my window & [in] my bedroom, and I got my gun," Barone said.
"When I came around the corner, I saw the silhouette in my window, I pointed my weapon, I fired three times," he said.
Asked if he was shooting to kill, Barone said, "Yes."
The burglar Barone shot dead had a lengthy criminal record, and Barone had a permit for his gun. Even before the new law, he certainly could have been justified in using deadly force. But the "Castle Law" gives Barone added protection from criminal prosecution and even civil lawsuits.