The primary purpose of government under the social contract -- not the Constitution, but the theoretical social contract -- is to protect its citizens in their life, liberty and property from the predations of others, foreign and domestic, so that civilization may flourish. Citizens voluntarily give up some of their liberty and ultimately some of their property to achieve this security.
Alas, many have forgotten that most basic of principles. Case in point, literally, is the case of Brown v. Plata, in which the Supreme Court ordered the release of some 46,000 convicted criminals from California prisons. Because of what? Ultimately, prison overcrowding, which SCOTUS says in this case prevents a constitutionally adequate level of medical care. The pseudonymous Pajamas Media blogger Jack Dunphy explains in more detail.
Most people, including me, don't care about prison overcrowding. We want to be protected from people who will take our lives or our property. In fact, that is what government is supposed to do. I fail to see how this decision meets that most basic objective, just as I fail to understand how the exclusionary rule meets that objective.
In fairness, however, SCOTUS introduced the exclusionary rule after expressing exasperation that no other sanction seemed capable of preventing illegal searches by police. SCOTUS seems to have reached a similar level of exasperation in Brown, as Clayton E. Cramer explains, because California has been repeatedly dinged by courts to do something about its prison overcrowding and yet has done nothing.
But does prevention or easing of prison justify putting all of us in danger from released criminals? Does it justify the increased confidence felt by criminals that their crimes will not be punished because they know they can't be jailed?