Mrs. Jones calls the police and says Mr. Jones hit her. The police come and arrest him for domestic violence. Later Mrs. Jones changes her mind and says it didn’t happen and she won’t testify. What will happen?
The prosecutor can still proceed with his case against Mr. Jones by subpoenaing Mrs. Jones to court and forcing her to take the stand. Assuming she was telling the truth originally, she doesn’t have a privilege not to testify against her husband. If she refuses to testify, the District Attorney would seek to introduce her previous statements against the defendant. If Mrs. Jones said it didn’t happen, the DA could use the statements as prior inconsistent statements to convict Mr. Jones. Mrs. Jones could potentially face a perjury charge (lying under oath), however that is virtually never done. If Mrs. Jones refuses to testify at all and the judge finds she has no legal excuse for not testifying, she could be held in contempt of court and fined or jailed. Again, this almost never happens.
If Mrs. Jones wants to say the violence never happened but is afraid of perjury, she should consult a criminal defense attorney so he can say she as a legitimate reason for refusing to testify (self incrimination). If the prosecutor wants to proceed he would have to get a superior court judge to grant Mrs. Jones immunity.
Often people think that if they make a criminal charge against someone, and then change their mind, they can stop the process. That, however, is not usually the case. Once the police get involved the case takes on a life of its own and the outcome now is up to the police and the prosecutor. If Mrs. Jones says she wants to drop the charges in this domestic violence charge and doesn’t want to testify, the prosecutor can choose to do just that or he can choose to go forward anyway with his case against Mr. Jones. The case will not necessarily be dropped just because Mrs. Jones no longer wants to go forward.