Well, of course, the matter largely rests on whether the defensive force was used while the trespasser was inside the house or when he was outside the house. Given the decision to indict, I'd speculate that either the prosecutor's forensic evidence indicates the latter, or he's just decided he can make a compelling case to the jury regardless of the forensics evidence.
If the trespasser was in the house, the defendant has a lot going for him. Ohio O.R.C. 2305.40 "Owner, lessee, or renter of real property not liable to trespasser" , section (B), provides that the defendant is not liable to damages to the trespasser if (1) the owner was inside the dwelling, (2) the trespasser made, is making, or attempting to make unlawful entry, and (3) the owner used reasonably necessary force to repel the trespasser.
(The full text of O.R.C. 2305.40 can be found here: http://lawofselfdefense.com/blog/statute/ctd8ltn/
(Incidentally, note that of section (C) of O.R.C. 2305.40 applies important restrictions to section (B).
Of course, 2305.40 provides protection only against civil damages, not criminal charges. Also, it applies only while the owner is "repelling" the trespasser. Once the trespasser has been repelled (e.g., he is outside the home and no longer attempting to unlawfully enter), 2305.40 does not justify the use of further force.
In addition, O.R.C. 2901.05 "Burden of Proof--reasonable doubt--self defense" provides for a legal presumption (importantly, a rebuttable presumption) of the defendant having acted in self defense when using lethal force against a person who is unlawfully entering, or has entered, a residence. But as all self defense is fundamentally based on necessity, once the trespasser is outside and no longer attempting to unlawfully enter, he is no longer an imminent threat and no longer a legitimate target of lethal force--unless he somehow WAS continuing to represent an imminent threat, such as shooting into the home, etc.
(The full text of O.R.C. 2901.05 can be found here: http://lawofselfdefense.com/blog/statute/c84nky3/
Unfortunately, O.R.C. 2901.05 also affirms a real oddity of Ohio self defense law. In every other state, although the defendant bears the burden of production on self defense, once that burden of production has been met the state bears the burden of persuasion to prove beyond a reasonable doubt that the defendant did NOT act in self defense. In Ohio, and ONLY in Ohio, it is the defendant who bears the burden of persuasion to prove by a preponderance of the evidence that he DID act in self defense.
For sure, this will be an interesting case to keep on eye on.