Competency to Stand Trial

• Criminal trials, especially those in which a guilty verdict may result in the death penalty, must allow defendants to participate in their defense. Otherwise, a mistrial can result. The standard of competency to stand trial was established in 1960 in the Supreme Court decision Dusky vs. United States, in which the justices held that a defendant must have an ability to consult his attorney with "a reasonable degree of rational understanding." In some cases, criminals try to avoid trial by feigning mental illness. As a result, a court often employs a forensic psychologist to evaluate whether a defendant is truly incompetent. Additionally, forensic psychologists administer IQ tests, as patients with very low IQ's also may not be competent to stand trial.
  
  

Temporary Insanity

• A common defense may involve a claim that a defendant who is competent to stand trial committed a capital crime while in a state of mental delusion. The standard usually concerns whether a defendant was able to distinguish between right and wrong at the time of the offense. Generally, temporary insanity is not a "get out of jail free" card. However, it may be used as part of a guilty plea for a lesser -- i.e., non-capital -- charge. For the defendant to be able to make such a plea, a forensic psychologist should be able to make a compelling presentation to the court about the defendant's psychological history.
  
  

Sentencing Mitigation

• Even if a defendant is found competent to stand trial and ruled sane during the commission of the crime, a forensic psychologist may be employed by the defense to analyze the psychological and environmental origins of the subject's offense. Often, the forensic psychologist interviews the defendant and his family to get an overall picture of their background and character. The purpose of this evaluation usually is to cast the offender in a sympathetic light and explain the factors that led him to commit the capital offense. For instance, a defendant who suffered from extreme child abuse and poverty might be labeled a "product of his environment."
  
  

Risk Assessment

• One of the common arguments used by death penalty advocates considers whether a capital offender will kill again. Killing a dangerous offender may save other lives in the future. To address this argument, forensic psychologists conduct examinations that analyze the likelihood that the offender will commit more crimes. For instance, a husband who murders his wife for insurance money does not demonstrate the same pattern of violence as a serial killer. In other cases, the forensic psychologist analyzes the defendant's susceptibility to antisocial personality disorder, or APD. APD is a treatable illness that causes violent and aggressive behavior. The illness is listed in the authoritative "Diagnostic and Statistical Manual of Mental Disorders" and can be treated through therapy. As a result, rehabilitation is considered possible for capital offenders diagnosed with ADP.