"Get the law over here quick. One of them is in the front yard over there. He's down. The other one is running down the street. I had no choice. They came in the front yard with me man. I had no choice. Get somebody over here quick man."
In September of 2007, a Texas law known as the Castle Doctrine took effect, allowing home and business owners to use deadly force to defend their property, without the obligation to retreat. Horn referred to that law in the phone call.
"The laws have been changed in this country since September 1st and you know it and I know it. I have a right to protect myself."
But the man who authored the Castle Doctrine Bill, State Senator Jeff Wentworth of San Antonio, says Horn's actions fell well outside the scope of that law.
"The Castle Doctrine applies if you're in your home or your motor vehicle and your place of business and you're being attacked within one of those three places. The Castle Doctrine is just not involved in this case. There are other provisions of the penal code that do apply where someone is stealing personal property of a third party, but the Castle Doctrine is not applicable in this case."
"Really the best bet that Joe Horn has is an argument that he is protecting the private property of another person when it can't be protected in another way."
Adam Gershowitz is an associate professor of law at South Texas College of Law here in Houston. He says Texas law, in some cases, does allow for the protection of someone else's property.
"There is a provision in the Texas code that says you can protect private property with force if there is no other reasonable way to do so. In other words, he's allowed to take action to protect private property if there's no reasonable belief that the crime is going to be stopped in another way."
The proceedings of the grand jury are secret and nobody from the Harris County District Attorneys office is commenting about the case.