A fight occurred between person 1 and person 2. Person 1 and Person 2 were kicked out of a bar for almost fighting, they go outside, and Person 1 walks up to Person 2 and offers an apology, and puts his hand out to shake his hand. Person 2, does not accept it, and 1 minute later, pushes Person 1. Person 1 then responds by throwing one punch, in self defense. Person 2 now has an injury to his face.
What charges can be brought against person 1, or person 2? Are civil charges likely to be filed against person 1 if person 2 was injured?
Either party can be charged with assault and battery (PC sections 240 and 242). However, it is unlikley charges would be brought given the facts that you have suggested. You are allowed the right of lawful self-defense, and you can use that force that is reasonably necessary to avoid imminent bodily injury or harm. In my experience neither the San Diego City Attorney nor the San Diego County District Attorney's office would pursue a claim like this. Remember too, the prosecution would have to prove the case beyond a reasonable doubt to all 12 jurors. A difficult task with the facts you've set out.
As for the civil matter, again, either party could bring a cause of action against the other ('charges' as you wrote in your question). Much like the answer to the criminal part of your question though, it would seem to be a waste of time on either party's part to pursue it. Unless Person 2 has sustained some substantial injury and has some independent witnesses to the event, it would not be worth the time or the money involved to try and recover civil damages. Person 1 is allowed lawful self-defense, thus a legal bar to the cause of action if the jury thinks Person 1 had a reasonable apprehension of imminent bodily harm. Even if Person 1's self defense was improper, then what are Person 2's damages? By that I mean, if the injuries were not significant then their economic value in terms of things like medical costs and pain and suffering would be likewise small. The burden of proof for this type of case is called a 'preponderance of the evidence', meaning that amount of evidence that would prove the elements of the offense slightly more than the contrary position. You could roughly analogize that to saying '50.1%' of the evidence.
Person One and Person Two could both be charged with be drunk and disorderly. If Person Two files a criminal complaint Person One can be charged with Assault and Battery a misdemeanor offense. The charge could be more serious depending on the nature and the extent of the injuries Person Two has received. The only way a civil complaint would be filed is if Person Two on his own or with an attorney filed a civil complaint, (lawsuit), against Person One. Civil lawsuits are not brought by the state they are private causes of action. While the incident, as you describe it, may give rise to a defense of self-defense you need to understand that self-defense is a factual defense and not a legal defense. This means that assuming you were acting in self-defense neither the police nor prosecution needs to believe it, or accept it. It is not even for the judge to say whether or not you were acting in self-defense. As a factual defense it is for the jury to decide whether your actions were in self-defense. Most likely the state would decline prosecution for the reasons that it sounds like it may have been a situation where the two of you were mutual combatants. The best advice I can give you at this point in time is to perhaps try to assemble a list of names and addresses of people who were at the bar who could corroborate, (if necessary), as to what was going on in the bar between the two of you. If place under arrest and charged you should probably decline to make a statement without a lawyer present or consulted.
I agree with the sound assessment and suggestions of my colleague. If you (or another person you are writing about) are charged, do not try to explain your side of the story, as anything you say can be used against you, even something as simple as indicating that you were at the scene of the incident. If you are charged, consult immediately with a CA criminal defense lawyer before you make any decisions about the case. Good luck.
DISCLAIMER: I do not practice law in your State. This answer is provided solely for informational purposes only. This answer does not constitute legal advice, create an attorney-client relationship, or constitute attorney advertising.