(1)A person other than a police officer who is charged with the duty of conducting an investigation with a view to it being ascertained—
(a)whether a person should be charged with an offence, or
(b)whether a person charged with an offence is guilty of it,
shall in discharging that duty have regard to any relevant provision of a code which would apply if the investigation were conducted by police officers.
(2)A failure—
(a)by a police officer to comply with any provision of a code for the time being in operation by virtue of an order under section 25, or
(b)by a person to comply with subsection (1),
shall not in itself render him liable to any criminal or civil proceedings.
(3)In all criminal and civil proceedings a code in operation at any time by virtue of an order under section 25 shall be admissible in evidence.
(4)If it appears to a court or tribunal conducting criminal or civil proceedings that—
(a)any provision of a code in operation at any time by virtue of an order under section 25, or
(b)any failure mentioned in subsection (2)(a) or (b),
is relevant to any question arising in the proceedings, the provision or failure shall be taken into account in deciding the question.