Mental health legislation sits astride two control systems, the psychiatric and the penal, yet the two systems have different methods and aims. One is concerned with treating mentally disordered according to the medical paradigm, the other with inflicting suffering according to the principles of retribution or deferrence – depending on one's philosophical view of punishment (see Bean, 1981). One claims a scientific approach, the other is avowedly moral. One emphasises clinical judgments borne out of the expertise of the physician, the other the requirements of procedural rules and the evaluation of evidence within the dictates of judicial authority. The control systems touch at the points where the mentally disordered commit crimes or where criminals become mentally disordered, requiring each system to accommodate the other.

It was once fashionable to claim that all criminals were mentally disordered, neurotic perhaps rather than psychotic, and that treatment rather than punishment should dominate. Few seriously entertain such views nowadays although strands of that argument appear after the commission of certain heinous and bizarre crimes. Then, it is suggested, the criminal must be mentally deranged in some way. Mental disorder thus becomes associated with incredulity and mindless crime. Other than that, the general view is that most criminals are free from mental disorder and most mentally disordered are free from criminality. Whereas it was once fashionable to assert the ‘crime of punishment’ nowadays criminologists are more likely to talk of the ‘crime of treatment’ – the former on the basis that suffering should be substituted by treatment, the latter that treatment offers indeterminacy in sentencing and loss of procedural safeguards.