mentor graduate and undergraduate students. Many legal psychologists also conduct research in a more general area of psychology (e.g., social, clinical, cognitive) with only a tangential legal focus. Those legal psychologists who work in law schools almost always hold a JD in addition to a PhD Expert witnesses Psychologists specifically trained in legal issues, as well as those with no formal training, are often called by legal parties to testify as expert witnesses. In criminal trials, an expert witness may be called to testify about eyewitness memory, mistaken identity, competence to stand trial, the propensity of a death-qualified jury to also be "pro-guilt", etc. Psychologists who focus on clinical issues often testify specifically about a defendant's competence, intelligence, etc. More general testimony about perceptual issues (e.g., adequacy of police sirens) may also come up in trial. Experts, particularly psychology experts, are often accused of being "hired guns" or "stating the obvious". Eyewitness memory experts, such as Elizabeth Loftus, are often discounted by judges and lawyers with no empirical training because their research utilizes undergraduate students and "unrealistic" scenarios. If both sides have psychological witnesses, jurors may have the daunting task of assessing difficult scientific information. Policy making and legislative guidance Psychologists employed at public policy centers may attempt to influence legislative policy or may be called upon by state (or national) lawmakers to address some policy issue through empirical research. A psychologist working in public policy might suggest laws or help to evaluate a new legal practice (e.g., eyewitness lineups). Advisory roles Legal psychologists may hold advisory roles in court systems. They may advise legal decision makers, particularly judges, on psychological findings pertaining to issues in a case. The psychologist who acts as a court adviser provides similar input to one acting as an expert witness, but acts out of the domain of an adversarial system. Amicus briefs Psychologists can provide an amicus brief to the court. The American Psychological Association has provided briefs concerning mental illness, retardation and other factors. The amicus brief usually contains an opinion backed by scientific citations and statistics. The impact of an amicus brief by a psychological association is questionable. For instance, Justice Powell once called a reliance on statistics "numerology" and discounted results of several empirical studies. Judges who have no formal scientific training also may critique experimental methods, and some feel that judges only cite an amicus brief when the brief supports