In section 2 of the Homicide Act 1957 (c. 11) (persons suffering from diminished responsibility), for subsection (1) substitute—

“(1)

A person (“D”) who kills or is a party to the killing of another is not to be convicted of murder if D was suffering from an abnormality of mental functioning which—

(a)

arose from a recognised medical condition,

(b)

substantially impaired D's ability to do one or more of the things mentioned in subsection (1A), and

(c)

provides an explanation for D's acts and omissions in doing or being a party to the killing.

(1A)

Those things are—

(a)

to understand the nature of D's conduct;

(b)

to form a rational judgment;

(c)

to exercise self-control.

(1B)

For the purposes of subsection (1)(c), an abnormality of mental functioning provides an explanation for D's conduct if it causes, or is a significant contributory factor in causing, D to carry out that conduct.”