The Eighth Amendment requires that state and federal prison systems provide at least “the minimal civilized measure of life’s necessities.” (Rhodes v. Chapman, 452 U.S. 337 (1981); see Do prison inmates have any rights?) Because this rule is so vague, prisons can be deficient in a variety of ways yet still meet minimum constitutional standards. (Depending on the jurisdiction, however, there may be laws that hold prison authorities to higher standards than those the federal Constitution imposes.)
To prove that prison conditions are cruel and unusual under the U.S. Constitution, prisoners must show that they were forced to live with seriously hazardous or oppressive conditions; this is an objective test that looks at the conditions themselves. They must also establish that prison officials were deliberately indifferent to the conditions, a subjective question that considers the state of mind of the officials responsible for them. (Wilson v. Seiter, 501 U.S. 294 (1991).)
Examples of inadequate prison conditions include:
A condition may be improper even if it affects only a small group of prisoners. For example, prison officials may violate both the First (free exercise of religion) and the Eighth (freedom from cruel and unusual punishment) Amendments if they do not provide pork-free meals to prisoners whose religions forbid eating pork, even if the non-pork-eaters make up a minority of the population.