One thing is absolutely for certain, you do not have the right to use deadly force in the defense of uninhabited property. Well, in most cases and in most places.
Even if the teenage car thief invaded the dwelling (entered the garage) to steal the car, as soon a he started leaving and began backing down the driveway with the car, he can longer be considered a threat to attack someone inside the dwelling, and deadly force can not be used to protect the stolen car. Even if you caught him inside the garage and interrupted the theft, you couldn't use deadly force. You have to have a reasonable belief that the car thief actually intends harm on you or those inside the dwelling in order to use deadly-force.
Even non-lethal force cannot be used on a thief or burglar,
if some other, reasonable means would have the same effect (like firing a gun into the ground, instead of into the burglar).
The only place I know of (and there may be more) that allows the use of deadly force to protect your uninhabited property, or even someone else's property, when the person reasonably believes deadly force is necessary to prevent someone from committing arson, burglary, robbery, aggravated robbery, theft during the nighttime, or criminal mischief during the nighttime, or to prevent a person from fleeing immediately after committing burglary, robbery, aggravated robbery, or theft during the nighttime
, is Texas.
If your dwelling, garage and car were in Texas, you'd likely not even be charged, but if you were you'd almost certainly be exonerated. One of the more famous cases was Pasadena, TX resident Joe Horn, who shot and killed two men who were burgling his neighbor's home. He was inside his home and saw the men burgling his neighbor's house. The entire incident was captured on the 911 call audio recording, and despite the dispatcher pleading him to not go out of his own house with his shotgun, he did just that.
"I'm not gonna let them get away with this [expletive]," he repeats to the dispatcher at one point, before then saying,
"I'll kill 'em."
After the 911 dispatcher again pleaded with him that property was not worth killing someone over, he told the dispatcher,
"Well, here it goes buddy, you hear the shotgun clicking and I'm going."
The next thing you hear on the recording is Horn yelling to the burglars,
"Move.... you're dead."
Immediately after hearing that, you hear the first of three shotgun blasts. Horn shot the two men in the back, killing both.
The Grand Jury refused to indict Horn, much to the horror of many people, including, I suspect, at least one philosopher.
Incidentally, the Grand Jury refused to indict him despite the fact that the two dead guys were illegal aliens. So there's another twist. LOL