The study developed from a research project that considered the assessment of the mentally abnormal offender at the arrest and prosecution stages in Scotland. Subsequently, the study was extended to consider some more general issues relating to mental abnormality and crime, using comparative references to the processing of mentally abnormal offenders in England and Wales. The two main aims of the Scottish project were, first, to identify measures for determining whether or not an alleged offender is suffering from a mental disorder which requires special treatment or handling and, second, to give the background information preliminary to improving legal and medical services for mentally abnormal offenders. A medico-legal framework is provided to assist in dealing with practical issues related to the mentally abnormal offender. Specific recommendations and general conclusions are offered in the following critical areas of decisionmaking: dangerousness and criminality, alcohol and drug-related offenses, and the socially inadequate offender. Some important issues considered relate to the use of discretionary powers in accord with the nature and purpose of criminal processing, individual rights, the use of medical facilities, and the accountability requirements governing criminal justice personnel. Appendixes cover relevant legislation in Scotland, England, and Wales, as well as the details of the Scottish research project. Endnotes, an index, and a selected 24-item bibliography are provided.