This is a serious charge, so if there is any possible way for the state to prove its case, then the charge will not be dismissed. The fact is that evidence other that witness statements can be used, if it exists. While the case would be stronger with their testimony, without it the case may still go forward. Further, if a person is subpoenaed to court nd they fail to show, then a warrant for failure to appear can be issued for their arrest. They then can face fines and possibly even jail time. Giving a false statement to the police is a chargeable offense. Also, you should be aware that in many states, even if the alleged victim of domestic violence  renounces any previouse statements that they may have made to the police, those statements may still be entered into evidence.