A ‘vulnerable’ adult is provided with an Appropriate Adult. From the Appropriate Adult website about vulnerable adults:
Put simply, a person is now vulnerable if a police officer has any reason to suspect the person may:
have difficulty understanding the full implications or communicating effectively about anything to do with their detention; or
have difficulty understanding the significance or things they are told, questions, or their own answers; or
may be prone to confusion, suggestibility, or compliance
may be prone to providing unintentionally unreliable, misleading or self-incriminating information.
Relevant conditions include (but are not limited to):
mental illness
learning disabilities
autistism spectrum conditions
brain injury.
The requirement for an AA still applies if:
there is no formal medical diagnosis or opinion from a heathcare professional
it is a minor offence
it is a terrorism offence
there is a legal advisor present
there is no organised AA scheme in the area
the person says they do not want an appropriate adult
The requirement for an AA does not apply if there is "clear evidence to dispel" the police officer's reason to suspect.