Psychological Syndromes and Criminal Responsibility

In criminal cases, evidence about psychological syndromes is typically introduced by the defense in support of insanity, self-defense, or imperfect self-defense claims and by the prosecution to show that a criminal act occurred. The admissibility of defense-proffered testimony about phenomena such as battered woman syndrome, combat stress syndrome, or XYY syndrome depends in the first instance on how insanity, self-defense, and other defensive doctrines are defined (the materiality issue). Additionally, this type of testimony, as well as prosecution-proffered evidence about phenomena such as rape trauma syndrome and abused child syndrome, must bear indicia of reliability (the probative value issue), add to the fact finder's knowledge (the helpfulness issue), and avoid distracting or confusing the fact finder (the prejudice issue). The ultimate admissibility decision involves consideration of the scope of the criminal law, the scientific methodology associated with the syndrome, the counter-intuitiveness of the evidence, and the role and capacities of juries