Psychological vulnerability (PV) is a term used to describe problems facing individuals with a mental illness or intellectual disability. PV poses considerable ethical and procedural problems for the criminal justice system. It is often difficult for law enforcement officers to identify PV individuals; PV individuals may have difficulties in understanding the legal process, and are especially vulnerable during police suspect interviews. This article reviews the characteristics, information processing, and communication difficulties facing individuals with a PV, and how these interact in the suspect interview context to challenge the collection of full and reliable accounts. We consider how police may mitigate some of these risks, through the identification of individuals with a PV in the first place, and through careful management of the interview, ensuring that as accurate account as possible can be obtained.