Each individual has needs that are particular to him or her. While the central need may be treatment for serious mental illness, other needs are frequently associated with it, including treatment for alcohol or substance abuse; treatment for HIV/AIDS or other illnesses or disorders; affordable housing; income assistance; and/or employment services. Not all needs are immediately evident, so a full assessment should be undertaken. This may certainly be focused on the need for mental health treatment and services, but it should by no means be limited exclusively to that arena. The use of illicit substances by a person with mental illness markedly increases his or her risk of contact with the criminal justice system and must be assessed.  The presence or absence of various supports in a person's life should always be thoroughly understood by treatment providers who are designing treatment plans. Similarly, as much as possible should be learned about the individual's history of treatment and incarceration. Not only will knowledge of this history be helpful in gaining a broad understanding of a person's condition and status, it could help in forging links with past or even current providers who can offer further insight useful in treatment. In building a person's history, mental health professionals should also try to learn whether or not the subject has been the victim of physical or sexual abuse. Understanding this part of a person's history can help immeasurably in designing effective services for that person.

Mental health treatment interventions are most effective when they are tailored to an individual's particular needs. It is clear that provider agencies must be staffed and organized to provide multiple interrelated services to the individuals they serve. For example, mental health agencies in many places have added staff expertise in the social supports needed by many clients with serious mental illness precisely so that services tailored to meet those needs can be offered. Substance abuse expertise is needed to address the large percentage of persons with co-occurring mental illness and substance abuse disorders.  By providing an array of services that can be tailored to each individual's needs, agencies are more likely to keep clients engaged, enabling many to develop the skills or contacts necessary for them to live successfully in the community.

Ideally, the public mental health system should function as part of a broader public health system that identifies problems in their early stages and takes steps to prevent their exacerbation. To do this effectively, the system must include a full array of services, including linkage with community resources traditionally seen as residing outside the mental health system. A community in which a full range of services is not available will find itself facing preventable problems, evident in the numbers of encounters between people with mental illness and components of the criminal justice system.

When clients find the services they receive to be helpful and meaningful, they are far more likely to continue them. For many people with mental illness, developing this sense of connection is extremely important. Because individually tailored services lead to more sustained engagement in mental health treatment, they are a critical link in preventing inappropriate criminal justice involvement.

A person with mental illness needs to gain access to appropriate services repeatedly.  Services are successful only if they are sustained over time. A provider agency's role, therefore, does not end with identifying services and providing referrals. Success of an intervention often rests on the level of support provided to a person with mental illness who is striving to follow his or her treatment plan. For the difficult-to-engage person who is most at risk for criminal justice involvement, this kind of support can often be quite intensive. Frequently, it means repeated outreach to the individual, often through such treatment models as Assertive Community Treatment (ACT) or intensive case management. For very ill individuals, it can mean access to acute care and inpatient services when needed. And it cannot be emphasized enough that such support must go well beyond purely treatment-related needs to supports such as housing, employment or education assistance, and transportation - supports that will enhance the likelihood of a person living successfully in the community.