Background In almost all countries worldwide, the first point of contact with the criminal justice system is with the police. A large proportion of these individuals may have vulnerabilities, such as mental health difficulties. Given the complexities associated with vulnerable suspects, such interviews may be compromised, which could lead to a miscarriage of justice. In England and Wales, the Police and Criminal Evidence Act (PACE) 1984 and its accompanying Codes of Practice lay down requirements for interviewing vulnerable suspects and provide for attendance of “appropriate adults” to support communication between police and the vulnerable suspect. To date, however, their role has been underresearched.

Aims/Hypotheses To explore the role of appropriate adults in police interviews and test the hypotheses, first, that appropriate adults more commonly remain passive during interview than expected from guidance and, second, that any interventions are more likely than not to follow examples in current guidance.

Methods Transcripts of police interviews conducted with suspects with possible mental disorder and an appropriate adult present (N = 27) were analysed using a specially developed coding framework.

Results Appropriate adults were significantly more likely to remain passive than to intervene, even when current guidance would suggest intervention. When they did intervene, however, such interventions were significantly more likely than not to follow from guidance than the vulnerable suspect's needs. Police and Criminal Evidence Act (PACE) 1984.