(1)Without prejudice to the general duty of the court at a trial on indictment to direct the jury on any matter on which it appears to the court appropriate to do so, where at such a trial—
(a)the case against the accused depends wholly or substantially on a confession by him ; and
(b)the court is satisfied—
(i)that he is mentally handicapped ; and
(ii)that the confession was not made in the presence of an independent person,
the court shall warn the jury that there is special need for caution before convicting the accused in reliance on the confession, and shall explain that the need arises because of the circumstances mentioned in paragraphs (a) and (b) above.
(2)In any case where at the summary trial of a person for an offence it appears to the court that a warning under subsection (1) above would be required if the trial were on indictment, the court shall treat the case as one in which there is a special need for caution before convicting the accused on his confession.
(3)In this section—
" independent person" does not include a police officer or a person employed for, or engaged on, police purposes ;
" mentally handicapped ", in relation to a person, means that he is in a state of arrested or incomplete development of mind which includes significant impairment of intelligence and social functioning; and
" police purposes " has the meaning assigned to it by section 64 of the [1964 c. 48.] Police Act 1964.