alongside that information, potentially incomplete, about the offender's mental health; their level of engagement with mental health services, if any; the impact upon the individual of being prosecuted or not prosecuted.  Not easy, is it?  What if you didn't know a nugget of information that was crucial about threats and risks? There may always be the possibility of a serious untoward event after someone is detained under mental health law.  This could come from the underlying condition itself, from the consequences of any restraint that became necessary or because of action taken by that person after arrest, for example to self-harm. It's always possible someone may die in custody, but it's very, very unlikely that they will.  How do we identify which should go to custody anyway and get an FME , which should go to A&E to see someone far faster or for an intervention that cannot be provided by an FME in a police station ? Both of these situations can benefit from the kind of risk model, above; simple though it is.  Determine the risk in the situation by balancing probability versus threat.  Deal with " unknown unknowns " according to the scale of risk you are determining.  So where you are pondering someone's safety in custody because of the potential for drugs or aggression to be masking a medical condition, call an ambulance and / or remove the person to A&E for advice in the paramedics think it is needed. If the risks and threats around