Reducing murder to manslaughter: whose job?

This paper compares two versions of the diminished responsibility defence, which reduces murder to manslaughter: the present statutory formulation and a proposed reformulation. The comparison confirms that evidence such as psychiatrists are commonly invited to give in murder cases takes them beyond their proper role. Paradoxically, although the two formulations mean essentially the same thing, the proposed change of wording must have the practical effect of subduing the psychiatrist's evidence. This conclusion leads to speculation about why psychiatrists are at present allowed so large a function in diminished responsibility cases and to some general observations about the role of the expert in relation to those of judge and jury.