Domestic Assault Charge, But With Unusual Circumstances

Location: State of Arizona, Pima County

I co-lease an apartment with my mother. She's recently brought my brother into the household, who is homeless. He doesn't work, doesn't pay rent, and at the time of the incident, was not on the lease. We have a tense relationship, and he's attempted repeatedly to worsen my relationship with my mother; my suspicion is that he's trying to remove me from the household and squat at the home as the new co-leaser.

My mother and I divide the food in the house to designate whose it is; hers on the right, mine on the left. My brother had honored this rule until the night of incident, where he put food items on my side of the freezer; I moved them to the opposite side.

Early the following morning, he barged into my room and loudly demanded to know if I'd eaten his pizza. I hadn't, and told him such. He made no effort to verify the matter, insisting on accusing me, until I finally went into the kitchen to proved I hadn't by retrieving the item, small personal pizza. His response was cornering me against the kitchen wall and screaming at me. Failing to talk him down, I eventually threw the item at him and hit him in the face, then made my way back to my room.

I would spend that day in jail on domestic assault charges. I've never once been in trouble with the law in any capacity, and have no criminal record; I haven't even had a traffic ticket, as I can't drive.

My brother, however, has several criminal charges, including assault, sexual assault, and reckless endangerment. It's my belief that given the circumstances, he used that experience to bait me into a conflict, and my attempt to separate myself from the situation gave him what he wanted.

My question is whether I have a defense in the matter; I don't want defending myself to be a mistake that follows me through the rest of my life. While I did physically intervene, it wasn't with the intent of harming him, but of stopping the situation. Given my past, and his, if I have a case, I believe it is by pitting my character against his own. It's also worth mentioning that his behavior hasn't changed at all, and indeed, he's talked my mother into himself being on the lease -- a curious decision were he to feel unsafe here. Given his current, now typical disheveled state of being unwashed and unshaven, I have reason to believe he also won't be attending the trial, but wish to be prepared if he does regardless.

Any advice is welcome and appreciated. Thank you.