Dropping charges against someone may sound easy, but it is in fact not within the power of an individual to do. Private individuals can be victims of crimes or they can be criminals, but they have no direct say in whether the state files or drops criminal charges.
Civil Cases and Dismissal
Anyone with a passing familiarity with the court system knows that some legal cases are civil and some are criminal. Civil cases happen when one individual or entity brings a case against another. These include divorce cases, medical malpractice cases, contract disputes, evictions or automobile accident litigation. Most people's lives brush up against a civil case at some point, even if it's only a small claims court dispute over a small loan that has not been repaid.
Since an individual can start a civil case by filing a petition or a complaint with the court, she can also drop a civil case. She might do this because she decides she can't win, she reaches an agreement with the other party or she just doesn't want to continue the case. She can file the appropriate papers in her state to withdraw her complaint and dismiss her action.
Criminal Cases and Dismissal
Criminal cases are a very different matter. An individual cannot file a criminal case in court; that's why all criminal cases are brought by "the People," as in The People of California vs. John Doe. The office of the district attorney or the prosecutor files criminal charges on behalf of the public.
Generally, it works like this: The police are called in by an individual to report that he was the victim of a crime. The police investigate, and if they believe there is enough evidence, they pass it over to the district attorney's office. There, the evidence is reviewed by attorneys and a decision is made whether to bring charges. Obviously, the testimony of the initial individual who witnessed the criminal activity is very important, but usually it is not the only evidence.
District Attorney Decides to File/Drop Charges
If a person calls in the police and gives a statement about an assault by her partner, the police are obligated to collect evidence and can pass the file to the district attorney's office. But it is neither the victim nor the police who decide whether criminal charges will be filed – that is up to the district attorney. The attorney in charge of reviewing the file may decide that there is not enough evidence to convict and opt not to file charges.
Similarly, it is the district attorney who decides whether to drop charges that have already been filed. The victim of the crime cannot make that decision. However, the district attorney may decide to drop the charges at the request of the victim in some cases like mistaken identity.
Refusing to Testify
Sometimes victims of crimes decide that they do not wish to proceed with the charges. This happens most often with victims of crimes like domestic violence or sexual assault, the most emotionally fraught charges in all of criminal law. The victim may decide to renew a relationship with the offender or may decide that it is just too painful to relive the crime in criminal court.
In most states, a judge can force a person to testify and hold her in contempt if she does not. However, in some states, like California, a person who claims to be a victim of domestic violence or sexual assault can refuse to testify against the accused.
While this can lead to the case being dismissed by the district attorney, there are no guarantees that this will happen. The prosecution can still use the victim’s statements, like 911 calls, that are admissible into evidence as excited utterances. And there may be medical evidence or third-party testimony sufficient to bring the matter to a jury.