Sometimes a person may regret calling the police and accusing someone of assault, with the result that assault charges are brought against the accused. Perhaps the person simply wanted to scare the alleged assaulter, or have the police mediate the argument. Whatever the reason, dropping assault charges is a difficult endeavour; when a criminal assault charge is made, the state is the case plaintiff. Only the state can drop the charges, although the initial accuser can request the prosecution drop the case. In a civil assault case, the plaintiff is the person claiming assault; that person may drop the charges at will.
Speak with the prosecution, if you are the initiator of assault charges in a criminal assault charge case. As the person who initially called the police or alleged assault, your testimony and cooperation will be key to the prosecution's case, even if you are not the legal plaintiff in the case. By indicating to the prosecution that you no longer wish to testify and give evidence to assault, the prosecution may find it difficult to pursue the case, due to lack of evidence, and you may force them to drop the charges.
File an affidavit of non-prosecution (ANP) with the court making the assault charges. This document indicates under oath to the court that you don't wish to pursue the charges and your reasons for doing so. This can be a legally tricky move, however. If you withdraw your charges against someone in an assault case, the prosecution has the option to prosecute you for bringing false charges against someone. And, since this affidavit is a legally-binding document, made under oath, it carries great weight with the court. For this reason, you should think very carefully before making accusations of assault and before seeking to have those charges dropped.
File a voluntary dismissal, if you are the plaintiff in a civil assault case. A civil case alleging assault is a lawsuit seeking damages for injuries caused during an assault. Unlike in a criminal assault case, you are the plaintiff in a civil assault case and may cancel your charges at any time during the case by filing for a voluntary dismissal of the case. Once assault charges are dropped, you cannot bring them back up again, unless another assault occurs. You should be absolutely certain you don't wish to pursue the charges before filing to have the case voluntarily dismissed.