Self defense is simply that, a defense. It does not, in and of itself, result in a dismissal of the charges or the release from custody. If the lawyer raises it to the prosecution, there are several possible alternatives that the prosecution has, such as a dismissal, the rejection of the defense by the prosecutor, the amendment of plea terms, etc. The possible dispositions and the position of the prosecutor need to be discussed with the lawyer, who is familiar with the case facts and the present status of the case. Good luck.
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I also agree with the other two responses and wish to add a bit about the time you family member has been in jail.
I have often heard it said that the wheels of justice do turn, but they turn slowly. It's true. If you have ever watched an episode of a crime and punishment show on TV, you would think it takes only a month or two from the time a crime happens until a criminal is brought to justice. In reality, it usually takes months, if not years.
For your family member, that means that he has been arrested and is in jail, probably waiting for the his attorney and the Assistant District Attorney to discuss his case between now and his next court date. The ADA is trying to see if the evidence collected by police, including witness statements and physical evidence like you might see on TV, match up with what your family member is telling his lawyer about what happened. While your family member might be telling the truth, there may be many other defendants may falsely claim self defense. Unfortunately, that also takes time.
Fortunately, if your family member does end up having to face charges in court, the time he is currently spending in jail would count against any time he could possibly sentenced to jail. I know that he states that this is self-defense, but I have also seen completed jail time used as a negotiating chip in previous cases. It is not *all* bad.
Best wishes to you and your family member in this case!
-Attorney Kristen Zorbini Bongard