Jurors must weigh specific data provided by witnesses with general principles derived from their commonsense experience to gauge the credibility of testimony. Many commentators argue that safeguards against eyewitness error and jury overconfidence are inadequate. Attempts to use instructions to improve jurors' abilities produce a dilemma. Jurors' strong, preexisting misconceptions seem to require strong, explicit, categorical corrective language; yet, the judge's categorical announcement of the answers to debated questions seem to threaten the fundamental basis of the jury trial. Some psychological research suggests that safeguards should be provided earlier in the trial process as eyewitnesses naturally integrate information brought up at trial with their own initial account of what happened. In a continuing debate over whether the psychologist is desirable for expert testimony, legal scholars, courts, and psychologists can be found on both sides of the debate. 40 references.