Defendant shot and killed her partner, Albert Hampton (“Hampton”), in their home in Fresno, California. When a police officer arrived she immediately surrendered, told him where the gun was, and admitted that she shot him. She explained, “He deserved it. I just couldn’t take it anymore. I told him to stop beating on me.” Defendant was charged with murder with personal use of a firearm. At trial, the defense asserted that Defendant shot Hampton in self-defense. They presented expert testimony on battered women’s syndrome from Dr. Lee Bowker, who stated that Defendant suffered from an extreme case of the syndrome. The court acquitted Defendant of first-degree murder and instructed the jury on second degree murder, voluntary manslaughter, involuntary manslaughter, and self-defense. The judge explained that for self-defense to be a complete or perfect defense to all charges, Defendant must have had an actual and reasonable belief that the killing was necessary. The judge further explained that an actual but unreasonable belief, imperfect self-defense, was a defense to murder but not to voluntary manslaughter. The judge instructed jurors that they could only use the battered women’s syndrome evidence to decide whether Defendant had an actual belief that the killing was necessary. The judge said the evidence could not be used to decide whether Defendant had a reasonable belief that the killing was necessary. The jury found Defendant guilty of voluntary manslaughter with personal use of a firearm. The court sentenced her to eight years in prison. The Court of Appeal affirmed the conviction. On appeal, the Supreme Court reversed the judgment. The Court held that the trial court erred when it instructed the jury that battered women’s syndrome evidence could not be used to determine whether Defendant had a reasonable belief that the killing was necessary. The Court opined that Defendant’s corroborated testimony had made a plausible case for perfect self-defense to all charges and the instruction error could have affected the verdict in a way adverse to Defendant.