Few of us would buy something if we did not need it for some purpose. We might be impulsive perhaps, but even impulsive purchases typically meet some real or perceived need. Of course, our reasoning may be flawed. But that in no way detracts from the notion that real or perceived needs drive much of our decision making, especially when the decisions entail large amounts of resources or sums of money.

A similar assertion can be made about criminal justice policies. That is, they presumably emerge from concern about a real problem, such as an increase in crime, or at least from what policy makers perceive to be a problem. Even so, what does it mean to say that there exists a sufficiently large problem, or that there exists a small but nonetheless important problem, as to create a need for a particular policy response, such as more prisons? What criteria should we use for assessing the amount of a social problem or the need for a particular policy response?

This chapter examines these questions by describing needs evaluations and what they entail. As will be detailed in this chapter, needs evaluations help to identify whether a problem exists and, in turn, whether and what type of a policy response is indicated. They provide guidance on prioritizing different problems. They point to research gaps that must be addressed before it can be determined that a policy response merits implementation and, if a response is warranted, which type.