The Court of Appeal defined abnormality of mind as a state of mind so different from that of ordinary human beings that the reasonable person would term it abnormal. It is wide enough to cover the mind’s activities in all its aspects, not only the perception of physical acts and matters and the ability to form a rational judgement as to whether an act is right or wrong, but also the ability to exercise willpower to control physical acts in accordance with that rational judgement.

D killed his wife after discovering she was having an affair.

Whilst sexual infidelity itself did not constitute a qualifying trigger, it could be considered if relevant to understand the gravity of a different qualifying trigger.