Murder case starting in 2 weeks under pre-castle doctrine (Feb 2007). No debate that D and V had some sort of vehicular confrontation. Facts of confrontation may vary. V follows D to D's home. D runs in home, V follows sometime thereafter. D and V struggle in home over rifle. Here's where fact really get varied. D and friends say struggle in D's bedroom, kitchen and out door over gun. D and V outside alone. Gun discharges accidently according to D's statement to cops at scene. D later lawyer's up. D's friends say do not see shooting. Suprise witness turns up months later. Happens to have been in house also but D and friends didn't say W was there originally. W first says same as D and friends but later says D and V got separated and V was pushed out door. D then opens door, raises rifle, shoots like a hunting a deer (we are in east texas) and closes door. W doesn't know where V is outside. W gets scared and runs to momma's house. V is dead. Single gunshot to back. About 15 ft or more away from D's house. No close contact wound or powder burn. We know D's story is BS.
Question: is D entitled to self-defense theory if he originally claimed gun accidentlly discharged during struggle over weapon? Can he have his cake and eat it too.

The idea behind self-defense is that the person admits they did the act and had the requisite mens rea, but was justified in doing so under the theory of self-defense. Simply grabbing the gun "in case I needed to use it in self-defense" is not the same as "I fired in self-defense." Claiming accident is the same as saying they never had a criminal mens rea.

That being said, if under the facts of your case (the evidence being strongly against any close contact and in favor of a distant shot to the back), what harm do you think would come in giving an instruction to the jury on it? If they believe that BS then your physical evidence wasn't that strong to begin with.

Based purely on the information here, Defendant isn't entitled to a self-defense instruction because there's no admission that he committed the offense but was justified. Accident and self-defense aren't the same thing. But if at trial there's some evidence that comes out showing that Defendant did purposely shoot Victim but did so out of self-defense, then you'd need the instruction, even if their main argument is accident.

I agree with Gretchen, though, that you're not likely to have a problem with it at trial so why risk a problem with excluding the instruction.