Forensic Neuropsychology’s growth is a direct result of the growth in the field of clinical neuropsychology. Over the past 40 years, clinical neuropsychology has established principles of brain-behaviour relations and valid and reliable methodologies for measuring these relationships. These principles and methodologies allow clinical neuropsychologists to provide the trier of fact with specialized information for use in the legal decision making process. Neuropsychological testimony is well-accepted in the courts. In a review of 200 appellate court cases in the 1980s, Richardson and Adams (1992) found that decisions in all jurisdictions upheld the right of a clinical neuropsychologist to testify about the presence of brain dysfunction.
In contrast to the apparent unanimity regarding a neuropsychologist’s ability to testify concerning the presence of brain dysfunction, there has been less acceptance of the clinical neuropsychologist’s ability to testify about the cause of brain dysfunction. Nonetheless, Richardson and Adams found that 9 of 11 jurisdictions allowed neuropsychological testimony regarding causation. Typically, challenges to neuropsychological testimony have been raised on the grounds that psychologists are not medical doctors and that the causal determination of brain damage is a medical issue.
Clinical neuropsychologists can be called upon to assist in both criminal and civil cases. Regardless of the legal venue, the primary responsibility of the clinical neuropsychologist participating in forensic work is to provide information based on scientifically-validated neuropsychological principles and clinical methodology that is pertinent to the Forensic Question at hand. Commonly, in a forensic neuropsychological evaluation, a battery of tests is used to assess neurocognitive functions in order to answer these questions. Different neuropsychologists may construct their batteries from different selections of tests. Some batteries are composed according to the patient’s presenting complaints and the referral question. Other neuropsychologists begin with a specific set of tests, seldom deviating from this selection, although often supplementing the basic battery. Regardless of which approach is used, the results of the battery of tests often form the primary basis for the neuropsychological testimony in answering the Forensic Questions.