Mens Rea
To hold a person criminally responsible before law, mens rea must be established. Mens rea, from the Latin mens, meaning mind and rea, meaning guilty or guilty mind, is presently established according to several criteria.
Consideration for criminal responsibility can involve intent, knowledge or recognition of one's own acts, recklessness (irresponsible acts that put at risk or cause harm to a third part's well being or property), and negligence (willful omission in exercising the proper care of a person or property under the individual's responsibility, or the failure in providing a service as required by law under the circumstances). Mens rea is therefore the basis of legal accountability both in civil and criminal courts. In its absence, or if the offender's mens rea is diminished or impaired due to a mental disorder or another circumstance, the offender cannot be blamed or punished by his act or omission. In other words, the prosecution has to prove that the accused not only committed the offense, but also that the individual had the required state of mind to be legally responsible for the act.
Criminal responsibility is often questioned by defense lawyers on the grounds of temporary or chronic insanity. These grounds require the assessment of the defendant by forensic psychiatrists and the testimony of the psychiatrist in court. As a general rule, criminal offenders diagnosed as not responsible for their acts by reason of mental retardation or a psychiatric disorder, will be, at the court's discretion, subjected to compulsory confinement or hospitalization in a psychiatric institution for treatment. Legislation of each country regulates the extension, duration, termination, and supervision of treatment and reclusion of mentally ill offenders.
Because criminal responsibility implicates liability for punishment, the establishment of mens rea has been required in some countries for centuries. This legal principle has been known and required since the thirteenth century in some European countries such as Italy and Scotland. However, the admission of expert witnesses to assess mental capacity in criminal courts is a relatively recent practice that encountered much resistance during the last decades of the nineteenth century, when psychiatry was still in its infancy. In the United Kingdom, the Report of the Royal Commission on Capital Punishment stated that criminal responsibility should not be founded solely on legal principles, but also on the establishment of moral responsibility. The report defined moral responsibility as the ability of a person to know that their action was legally and morally wrong, according to the criminal law and the moral standards of the community. Much controversy existed about whether or not it was possible to establish such moral responsibility. The English physician and philosopher John Locke (1632–1704), for instance, argued that a person's actions are completely separated from his thoughts. Later the English Lady Wootton stated that not even science could provide any answers to the questions concerning the moral responsibility of an individual. In 1863, an English judge recommended jurors to "not be deprived of the exercise of your common sense because a gentlemen comes from London and tells you scientific sense."
The common law test to establish criminal responsibility, known as M'Naghten rule, originated in Great Britain in the nineteenth century and was later applied in the United States. Daniel M'Naghten was what is now defined as a paranoid schizophrenic who murdered the secretary to British Prime Minister Robert Peel in 1843. M'Naghten was acquitted under the grounds of delusion and lack of control over his actions, and sent to a mental institution instead of receiving the capital penalty. His case, in addition to other previous similar judicial decisions, established by common law the M'Naghten rule, which assumed that if an individual could distinguish right from wrong, he or she was not insane and therefore, was criminally responsible. Conversely, if the offender was not able to make such distinction, insanity was established and acquittal was required.
Some English jurists have criticized the ambiguities of the standards for insanity under the M'Naghten rules and have proposed three parameters for acquittal of criminal responsibility: the illegality standard, the subjective moral standard, and the objective moral standard. The illegality assumed that if the offender lacked the capacity to understand that his acts were against the law, he could not be held accountable for those actions. The second standard stated that those offenders suffering from a disease of the mind that caused a delusional belief of being morally justified in their actions or that God dictated their acts, should be considered mentally insane and not criminally responsible. The third standard assessed the capacity for understanding the social moral standards and the capacity to abide by them. The United States, Tasmania, and Queensland have added another parameter to these rules, that of partial insanity and irresistible impulse, which characterize diminished responsibility, implying that if a person was under a temporary delusion, even if not insane, mitigation of responsibility (and penalty) could be considered by the defense. In Great Britain, however, due to the many cases of acquittal and even release of offenders who made attempts against the lives of members of the royal family and other political personalities, such revisions of the test by the Atkin Committee on Insanity and Crime in 1923, and by the Royal Commission on Capital Punishment in 1953 were rejected by the Judiciary. Queen Victoria even tried to change the Trial of Lunatics Act of 1883 to an "insane but guilty" connotation. However, the common law was maintained, with the special verdict of insanity implying a qualified acquittal, although not an absolute acquittal. More recently, the American model penal code required the establishment of a lack of substantial capacity by the offender to conform his behavior to the law and admit insanity defense pleas.
Diminished responsibility due to partial insanity existed in Scottish penal law since the seventeenth century. It did not imply acquittal, but only penalty mitigation, by changing the charge from murder to manslaughter. Partial insanity was defined as an abnormality of the mind arising from a condition of arrested or retarded mental development, or a disease or injury that significantly impaired mental responsibility for acts or omissions in relation to a killing. Therefore, manslaughter opened a wide range of possibilities for courts, which ranged from conviction for life, or compulsory commitment to a mental institution, to absolute acquittal.
It is important to emphasize that all the above descriptions and definitions of insanity were non-scientific in nature and the tests were merely cognitive, as medical psychiatry was still in its infancy. The first attempts to assess criminal responsibility in courts used non-specialist physicians and even apothecaries as expert witnesses, during the late nineteenth and early twentieth centuries, both in England and the U.S., with convictions or acquittals due much more to lawyers' rhetorical skills than to sound scientific data. When psychiatrists began to serve as expert witnesses, a standardized psychiatric evaluation procedure was not still in use, often giving rise to allegations of inferential, inconclusive diagnoses from both the prosecution and the defense.
Forensic psychiatry is a relatively recent specialty that differs from clinical psychiatry in its objectives. While clinical psychiatry aims at diagnosing and treating neuropsychiatric disorders, forensic experts must establish to courts whether an offender was, at the time the offense was committed, mentally impaired or sane. In the first case, a precise diagnosis and the explanation of how the mental condition interferes with the cognitive, emotional, and behavioral capacities of the offender is necessary. Forensic psychiatry is a sub-field of psychiatry that requires special training in order to perform specific types of clinical assessments and diagnoses, such as retrospective, transversal, or prospective assessments to prosecutors, defense lawyers, probation boards, judges, and police investigators. The adoption of psychiatric diagnostic guidelines by several countries in the last 20 years gave the forensic experts a new level of credibility in courts, thanks to the advances in neurosciences and diagnostic resources and technologies.
A more clear description in the last 30 years of biological factors associated with each psychiatric disorder and the detailed description of related symptoms, led to the publication of the Clinical Descriptions and Diagnostic Guidelines and the Diagnostic Criteria for Research of psychiatric disorders by the World Health Organization (WHO), which is used by several countries around the world to establish forensic criminal responsibility. In the United States, the American Psychiatric Association (APA) is responsible for the guidelines used by forensic psychiatrists, published under the title Diagnostic and Statistical Manual of Mental Disorders. WHO and APA guidelines are regularly updated to incorporate new scientific information and diagnostic techniques. Such advances and improvements in science and law released the task of establishing mens rea from the realm of conjecture and philosophical arguments, and gave it the status of an objective evidence-based scientific field. In many countries, forensic psychiatry has become a field of expertise apart from clinical psychiatry, and a qualified psychiatrist is the only expert witness recognized in court to establish criminal responsibility.