In cases involving serious assault or homicide, convictions often are difficult to obtain. The defense may be less willing to prosecute, and the prosecution may not have much to bargain with. Often the victim is the only witness and may make a poor witness because of the effect of the battering on her self-esteem or because she fears retribution. In such cases an expert can be called upon to provide additional support for the victim and help her overcome her reluctance to testify. Expert witnesses such as shelter staff can corroborate the witness' injuries and help the court understand some of the dynamics of the victimization that contribute to this reluctance to testify. In addition, psychological expert testimony outlining the characteristics of batterers and the dynamics of the battering relationships can strengthen the case against the offender and can aid in rebutting heat-of-passion and diminished capacity defenses. Further, expert testimony utilizing research results can explain the symptoms of battered woman syndrome and help rebut assertions of victim crime precipitation. Finally, in cases involving homicide, expert witnesses can provide information based on previous contacts with the victim or offender or can examine the validity of State evidence and the State's witnesses to corroborate the existence of domestic violence. 50 references.