Story of Psychology - Morton Hunt [421]
—act as observer and adviser to a judge and attorneys when they interview a child to determine his or her competence as a witness.
—obtain evidence in sexual abuse cases from children too young to testify in court. Using methods borrowed from child therapy, psychologists watch children play with dolls and look for the enactment of activities similar to those of the alleged crime.
—interview and test a criminal suspect pleading the insanity defense. That defense is successfully used far less often than the public supposes. Surveys have found that the public thinks about 40 percent of criminals use the insanity plea and that a third of them succeed, but in 1991 a major eight-state study commissioned by the National Institute of Mental Health found that less than 1 percent of county court cases involved the insanity defense, and that of those, only around one in four was successful.78
Certain other applications of psychology to justice processes are of more doubtful value, since they are not well accepted by court professionals or have uncertain outcomes. Cases in point:
Predictions of dangerousness: Probation boards often ask psychologists to predict how likely it is that a prisoner convicted of a violent crime will commit additional violent crimes if released. Willie Horton gave a bad name to the psychological evaluation of future violence, as have other killers who, freed, have killed again.
A much-cited review of five studies of predictions of violence found that the clinicians were correct in their predictions only a third of the time.79 (Many of their errors, however, were innocuous “false positives”—predictions of violence by an individual who, after being released, did not commit further acts of violence.) The U.S. Supreme Court reviewed the capital conviction of one Thomas Barefoot, whose lawyer claimed that testimony predicting Barefoot’s future violence should not have been considered in deciding his sentence. In 1983 the Supreme Court disagreed, holding that such testimony is not necessarily unreliable.80 But even the American Psychiatric Association argued in an amicus curiae brief that predictions of dangerousness are wrong too often to be used where a death penalty is involved, and throughout the 1980 and 1990s, most mental health professionals maintained that dangerous behavior could not be predicted. Some recent studies, however, suggest that if certain basic rules were followed, clinicians could indeed predict dangerousness in certain situations—a not thoroughly reassuring conclusion.81
Lie detector tests: The usefulness and validity of lie detector tests have been debated for many years by psychologists, legislators, lawyers, judges, and the press. As we have seen, anxiety about lying, particularly when the subject is asked questions containing key words or phrases related to the crime, will produce accelerated heart rate, accelerated breathing, and increased skin conductance, all of which the polygraph clearly shows. But the large research literature on the subject provides a great deal of evidence against, as well as for, the theory. An analysis of ten careful studies of the use of lie detection equipment showed that polygraphs do 64 percent better than pure chance—a lot better, but still far too inaccurate to warrant their use as evidence.82 That 1985 conclusion has been reaffirmed repeatedly. In 2002 an expert panel convened by the National Academy of Sciences found no scientific evidence to warrant the use of polygraphs on a regular basis, pointing out that while thousands of employees of the FBI, CIA, and other governmental agencies have been given