//Fred West required an appropriate adult due to his inability to read or write.
West left school at the age of 15 which resulted in him remaining largely illiterate.
In police interviews, when suspects are given documents they need to be able to fully understand what they are being shown.
Combined with the severity of the charges made against him, police deemed it necessary for West to have someone supporting him through the interrogation process. //
https://www.thesun.co.uk/news/12746298/why-did-fred-west-need-an-appropriate-adult/