As to the meaning of misconduct and deficient professional performance, Jackson J addressed some aspects of these concepts in Calhaem v General Medical Council  EWHC 2606 (Admin);  LS Law Medical 26:
"(1) Mere negligence does not constitute "misconduct" within the meaning of section 35C(2)(a) of the Medical Act 1983. Nevertheless, and depending upon the circumstances, negligent acts or omissions which are particularly serious may amount to "misconduct".
(2) A single negligent act or omission is less likely to cross the threshold of "misconduct" than multiple acts or omissions. Nevertheless, and depending upon the circumstances, a single negligent act or omission, if particularly grave, could be characterised as "misconduct".
(3) "Deficient professional performance" within the meaning of 35C(2)(b) is conceptually separate both from negligence and from misconduct. It connotes a standard of professional performance which is unacceptably low and which (save in exceptional circumstances) has been demonstrated by reference to a fair sample of the doctor's work.
(4) A single instance of negligent treatment, unless very serious indeed, would be unlikely to constitute "deficient professional performance".
(5) It is neither necessary nor appropriate to extend the interpretation of "deficient professional performance" in order to encompass matters which constitute "misconduct".Absent from this consideration, because it was not relevant, was that culpable conduct under section 35C need not occur in relation to clinical treatment. An obvious example is sexual misconduct with patients; another could arise from giving expert evidence in court (e.g. Meadow v General Medical Council  EWCA Civ 1390;  QB 462).
5th Edition » | Chapter 18