Guidance to commissioning authorities on the appointment of investigating officers is contained in Section 3.B of Prison Service Order (PSO) 1300—Investigations.
In particular it states that
“Investigators must have no significant conflicts of interest with the matter or persons under investigation. Should such conflicts arise within the course of an investigation the matter must be immediately referred to the commissioning authority”.
This is a mandatory requirement and commissioning authorities must ensure that this requirement is met.